Photopolymerizable compositions including a urethane component and a monofunctional reactive diluent, articles, and methods

ABSTRACT

The present disclosure provides a photopolymerizable composition. The photopolymerizable composition includes at least one urethane component, at least one monofunctional reactive diluent, an initiator, and optionally an inhibitor. The present disclosure also provides an article including the reaction product of the photopolymerizable composition. Further, the present disclosure provides a method of making an article. The method includes (i) providing a photopolymerizable composition and (ii) selectively curing the photopolymerizable composition to form an article. The method optionally also includes (iii) curing unpolymerized urethane component and/or reactive diluent remaining after step (ii). Further, methods are provided, including receiving, by a manufacturing device having one or more processors, a digital object comprising data specifying an article; and generating, with the manufacturing device by an additive manufacturing process, the article based on the digital object. A system is also provided, including a display that displays a 3D model of an article; and one or more processors that, in response to the 3D model selected by a user, cause a 3D printer to create a physical object of an article.

TECHNICAL FIELD

The present disclosure broadly relates to articles including a urethanecomponent and at least one monofunctional reactive diluent, and methodsof making the articles, such as additive manufacturing methods.

BACKGROUND

The use of stereolithography and inkjet printing to producethree-dimensional articles has been known for a relatively long time,and these processes are generally known as methods of so called 3Dprinting (or additive manufacturing). In vat polymerization techniques(of which stereolithography is one type), the desired 3D article isbuilt up from a liquid, curable composition with the aid of a recurring,alternating sequence of two steps: in the first step, a layer of theliquid, curable composition, one boundary of which is the surface of thecomposition, is cured with the aid of appropriate radiation within asurface region which corresponds to the desired cross-sectional area ofthe shaped article to be formed, at the height of this layer, and in thesecond step, the cured layer is covered with a new layer of the liquid,curable composition, and the sequence of steps is repeated until aso-called green body (i.e., gelled article) of the desired shape isfinished. This green body is often not yet fully cured and must,usually, be subjected to post-curing. The mechanical strength of thegreen body immediately after curing, otherwise known as green strength,is relevant to further processing of the printed articles.

Other 3D printing techniques use inks that are jetted through a printhead as a liquid to form various three-dimensional articles. Inoperation, the print head may deposit curable photopolymers in alayer-by-layer fashion. Some jet printers deposit a polymer inconjunction with a support material or a bonding agent. In someinstances, the build material is solid at ambient temperatures andconverts to liquid at elevated jetting temperatures. In other instances,the build material is liquid at ambient temperatures.

One particularly attractive opportunity for 3D printing is in the directcreation of orthodontic clear tray aligners. These trays, also known asaligners or polymeric or shell appliances, are provided in a series andare intended to be worn in succession, over a period of months, in orderto gradually move the teeth in incremental steps towards a desiredtarget arrangement. Some types of clear tray aligners have a row oftooth-shaped receptacles for receiving each tooth of the patient'sdental arch, and the receptacles are oriented in slightly differentpositions from one appliance to the next in order to incrementally urgeeach tooth toward its desired target position by virtue of the resilientproperties of the polymeric material. A variety of methods have beenproposed in the past for manufacturing clear tray aligners and otherresilient appliances. Typically, positive dental arch models arefabricated for each dental arch using additive manufacturing methodssuch as stereolithography described above. Subsequently, a sheet ofpolymeric material is placed over each of the arch models and formedunder heat, pressure and/or vacuum to conform to the model teeth of eachmodel arch. The formed sheet is cleaned and trimmed as needed and theresulting arch-shaped appliance is shipped along with the desired numberof other appliances to the treating professional.

An aligner or other resilient appliance created directly by 3D printingwould eliminate the need to print a mold of the dental arch and furtherthermoform the appliance. It also would allow new aligner designs andgive more degrees of freedom in the treatment plan. Exemplary methods ofdirect printing clear tray aligners and other resilient orthodonticapparatuses are set forth in PCT Publication Nos. WO2016/109660 (Raby etal.), WO2016/148960 (Cinader et al.), and WO2016/149007 (Oda et al.) aswell as US Publication Nos. US2011/0091832 (Kim, et al.) andUS2013/0095446 (Kitching).

SUMMARY

Existing printable/polymerizable resins tend to be too brittle (e.g.,low elongation, short-chain crosslinked bonds, thermoset composition,and/or high glass transition temperature) for a resilient oral appliancesuch as an aligner. An aligner or other appliance prepared from suchresins could easily break in the patient's mouth during treatment,creating material fragments that may abrade or puncture exposed tissueor be swallowed. These fractures at the very least interrupt treatmentand could have serious health consequences for the patient. Thus, thereis a need for curable liquid resin compositions that are tailored andwell suited for creation of resilient articles using 3D printing (e.g.,additive manufacturing) method. Preferably, curable liquid resincompositions to be used in the vat polymerization 3D printing processhave low viscosity, a proper curing rate, and excellent mechanicalproperties in both the final cured article. In contrast, compositionsfor inkjet printing processes need to be much lower viscosity to be ableto be jetted through nozzles, which is not the case for most vatpolymerization resins.

Urethane (meth)acrylates are a class of raw materials that haveinteresting properties, for example an elongation of over 100% whencured, and very high toughness. But these resins also have a very highviscosity; at room temperature they are basically solids. Therefore,they only have been used in small amounts in photosensitive resinformulations for vat polymerization or stereolithography, and theproperties of these resins are dominated by the other components.

In a first aspect, a photopolymerizable composition is provided. Thephotopolymerizable composition includes a blend of (a) 30 to 70 wt. %,inclusive, of at least one urethane component and (b) 25 to 70 wt. %,inclusive, of at least one monofunctional reactive diluent. The at leastone monofunctional reactive diluent includes at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius. The photopolymerizable composition further includes (c)optionally at least one multifunctional reactive diluent in an amount of1 to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

In a second aspect, an article is provided including a reaction productof a photopolymerizable composition. The photopolymerizable compositionincludes a blend of (a) 30 to 70 wt. %, inclusive, of at least oneurethane component and (b) 25 to 70 wt. %, inclusive, of at least onemonofunctional reactive diluent. The at least one monofunctionalreactive diluent includes at least one monofunctional reactive diluenthaving a T_(g) of up to but not including 25 degrees Celsius. Thephotopolymerizable composition further includes (c) optionally at leastone multifunctional reactive diluent in an amount of 1 to 30 wt. %,inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

In a third aspect, a method of making an article is provided. The methodincludes (a) providing a photopolymerizable composition and (b)selectively curing the photopolymerizable composition to form anarticle. Optionally, the method further includes (c) curingunpolymerized urethane component and/or reactive diluent remaining afterstep (b). The photopolymerizable composition includes a blend of (a) 30to 70 wt. %, inclusive, of at least one urethane component and (b) 25 to70 wt. %, inclusive, of at least one monofunctional reactive diluent.The at least one monofunctional reactive diluent includes at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius. The photopolymerizable composition furtherincludes (c) optionally at least one multifunctional reactive diluent inan amount of 1 to 30 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition; (d) 0.1 to 5 wt. %,inclusive, of at least one initiator; and (e) an optional inhibitor inan amount of 0.001 to 1 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition.

In a fourth aspect, a non-transitory machine readable medium isprovided. The non-transitory machine readable medium has datarepresenting a three-dimensional model of an article, when accessed byone or more processors interfacing with a 3D printer, causes the 3Dprinter to create an article. The article includes a reaction product ofa photopolymerizable composition including a blend of (a) 30 to 70 wt.%, inclusive, of at least one urethane component and (b) 25 to 70 wt. %,inclusive, of at least one monofunctional reactive diluent. The at leastone monofunctional reactive diluent includes at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius. The photopolymerizable composition further includes (c)optionally at least one multifunctional reactive diluent in an amount of1 to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

In a fifth aspect, a method is provided. The method includes (a)retrieving, from a non-transitory machine readable medium, datarepresenting a 3D model of an article; (b) executing, by one or moreprocessors, a 3D printing application interfacing with a manufacturingdevice using the data; and (c) generating, by the manufacturing device,a physical object of the article. The article includes a reactionproduct of a photopolymerizable composition including a blend of (a) 30to 70 wt. %, inclusive, of at least one urethane component and (b) 25 to70 wt. %, inclusive, of at least one monofunctional reactive diluent.The at least one monofunctional reactive diluent includes at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius. The photopolymerizable composition furtherincludes (c) optionally at least one multifunctional reactive diluent inan amount of 1 to 30 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition; (d) 0.1 to 5 wt. %,inclusive, of at least one initiator; and (e) an optional inhibitor inan amount of 0.001 to 1 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition.

In a sixth aspect, another method is provided. The method includes (a)receiving, by a manufacturing device having one or more processors, adigital object comprising data specifying a plurality of layers of anarticle; and (b) generating, with the manufacturing device by anadditive manufacturing process, the article based on the digital object.The article includes a reaction product of a photopolymerizablecomposition including a blend of (a) 30 to 70 wt. %, inclusive, of atleast one urethane component and (b) 25 to 70 wt. %, inclusive, of atleast one monofunctional reactive diluent. The at least onemonofunctional reactive diluent includes at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius. The photopolymerizable composition further includes (c)optionally at least one multifunctional reactive diluent in an amount of1 to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

In a seventh aspect, a system is provided. The system includes (a) adisplay that displays a 3D model of an article and (b) one or moreprocessors that, in response to the 3D model selected by a user, cause a3D printer to create a physical object of an article. The articleincludes a reaction product of a photopolymerizable compositionincluding a blend of (a) 30 to 70 wt. %, inclusive, of at least oneurethane component and (b) 25 to 70 wt. %, inclusive, of at least onemonofunctional reactive diluent. The at least one monofunctionalreactive diluent includes at least one monofunctional reactive diluenthaving a T_(g) of up to but not including 25 degrees Celsius. Thephotopolymerizable composition further includes (c) optionally at leastone multifunctional reactive diluent in an amount of 1 to 30 wt. %,inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

Clear tray aligners and tensile bars made according to at least certainembodiments of this disclosure were found to show low brittleness, highelongation, good resistance to water, and good toughness.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a process for building an article using thephotopolymerizable compositions disclosed herein.

FIG. 2 is a generalized schematic of a stereolithography apparatus.

FIG. 3 is an isometric view of a printed clear tray aligner, accordingto one embodiment of the present disclosure.

FIG. 4 is a flowchart of a process for manufacturing a printedorthodontic appliance according to the present disclosure.

FIG. 5 is a generalized schematic of an apparatus in which radiation isdirected through a container.

FIG. 6 is a block diagram of a generalized system 600 for additivemanufacturing of an article.

FIG. 7 is a block diagram of a generalized manufacturing process for anarticle.

FIG. 8 is a high-level flow chart of an exemplary article manufacturingprocess.

FIG. 9 is a high-level flow chart of an exemplary article additivemanufacturing process.

FIG. 10 is a schematic front view of an exemplary computing device 1000.

While the above-identified figures set forth several embodiments of thedisclosure other embodiments are also contemplated, as noted in thedescription. The figures are not necessarily drawn to scale. In allcases, this disclosure presents the invention by way of representationand not limitation. It should be understood that numerous othermodifications and embodiments can be devised by those skilled in theart, which fall within the scope and spirit of the principles of theinvention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As used herein, the term “hardenable” refers to a material that can becured or solidified, e.g., by heating to remove solvent, heating tocause polymerization, chemical crosslinking, radiation-inducedpolymerization or crosslinking, or the like.

As used herein, “curing” means the hardening or partial hardening of acomposition by any mechanism, e.g., by heat, light, radiation, e-beam,microwave, chemical reaction, or combinations thereof.

As used herein, “cured” refers to a material or composition that hasbeen hardened or partially hardened (e.g., polymerized or crosslinked)by curing.

As used herein, “integral” refers to being made at the same time orbeing incapable of being separated without damaging one or more of the(integral) parts.

As used herein, the term “(meth)acrylate” is a shorthand reference toacrylate, methacrylate, or combinations thereof, and “(meth)acrylic” isa shorthand reference to acrylic, methacrylic, or combinations thereof.As used herein, “(meth)acrylate-functional compounds” are compounds thatinclude, among other things, a (meth)acrylate moiety.

As used herein, “oligomer” refers to a molecule that has one or moreproperties that change upon the addition of a single further repeatunit.

As used herein, “polymer” refers to a molecule having one or moreproperties that do not change upon the addition of a single furtherrepeat unit.

As used herein, “polymerizable composition” means a hardenablecomposition that can undergo polymerization upon initiation (e.g.,free-radical polymerization initiation). Typically, prior topolymerization (e.g., hardening), the polymerizable composition has aviscosity profile consistent with the requirements and parameters of oneor more 3D printing systems. In some embodiments, for instance,hardening comprises irradiating with actinic radiation having sufficientenergy to initiate a polymerization or cross-linking reaction. Forinstance, in some embodiments, ultraviolet (UV) radiation, e-beamradiation, or both, can be used. Thermal initiation, using heat and athermal initiator, can also be employed to initiate polymerization of apolymerizable composition. A combination of actinic radiation andthermal radiation can be used.

As used herein, a “resin” contains all polymerizable components(monomers, oligomers and/or polymers) being present in a hardenablecomposition. The resin may contain only one polymerizable componentcompound or a mixture of different polymerizable compounds.

As used herein, a “compatibilizer” refers to a component (e.g., in apolymerizable composition) that improves the interfacial adhesionbetween two otherwise immiscible material phases. The compatibilizer ispresent throughout at least one phase, it is preferentially present atan interface between at least two of the phases, and it increases thecompatibility of at least two of the phases in the system. If the weightratio of the compatibilizer in the system is too high relative to theother phases, a portion of it may separately form a distinct phase.

As used herein, “miscible” refers to any (e.g., polymeric) blend havinga free energy of mixing less than zero, and “immiscible” refers to anyblend having a free energy greater than zero. A miscible polymer iscapable of forming a blend with a second material, which blend appearsto be a single phase with no apparent phase separation, and suchcapability may depend on the temperature of the blend.

As used herein, the terms “glass transition temperature” and “T_(g)” areused interchangeably and refer to the glass transition temperature of amaterial or a mixture. Unless otherwise indicated, glass transitiontemperature values are determined by Differential Scanning calorimetry(DSC). When the T_(g) of a monomer or oligomer is mentioned, it is theT_(g) of a homopolymer of that monomer or oligomer. The homopolymer mustbe sufficiently high molecular weight such that the T_(g) reaches alimiting value, as it is generally appreciated that a T_(g) of ahomopolymer will increase with increasing molecular weight to a limitingvalue. The homopolymer is also understood to be substantially free ofmoisture, residual monomer, solvents, and other contaminants that mayaffect the T_(g). A suitable DSC method and mode of analysis is asdescribed in Matsumoto, A. et. al., J. Polym. Sci. A., Polym. Chem.1993, 31, 2531-2539.

As used herein the term “hydrophilic-lipophilic balance” and “HLB” areused interchangeably and refer to a characterization of amphiphiliccharacter of a compound.

As used herein, “thermoplastic” refers to a polymer that flows whenheated sufficiently above its glass transition point and become solidwhen cooled.

As used herein, “thermoset” refers to a polymer that permanently setsupon curing and does not flow upon subsequent heating. Thermosetpolymers are typically crosslinked polymers.

As used herein, “occlusal” means in a direction toward the outer tips ofthe patient's teeth; “facial” means in a direction toward the patient'slips or cheeks; and “lingual” means in a direction toward the patient'stongue.

The words “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

In this application, terms such as “a”, “an”, and “the” are not intendedto refer to only a singular entity, but include the general class ofwhich a specific example may be used for illustration. The terms “a”,“an”, and “the” are used interchangeably with the term “at least one.”The phrases “at least one of” and “comprises at least” one of followedby a list refers to any one of the items in the list and any combinationof two or more items in the list.

As used herein, the term “or” is generally employed in its usual senseincluding “and/or” unless the content clearly dictates otherwise.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements.

Also herein, all numbers are assumed to be modified by the term “about”and preferably by the term “exactly.” As used herein in connection witha measured quantity, the term “about” refers to that variation in themeasured quantity as would be expected by the skilled artisan making themeasurement and exercising a level of care commensurate with theobjective of the measurement and the precision of the measuringequipment used. Also herein, the recitations of numerical ranges byendpoints include all numbers subsumed within that range as well as theendpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

As used herein as a modifier to a property or attribute, the term“generally”, unless otherwise specifically defined, means that theproperty or attribute would be readily recognizable by a person ofordinary skill but without requiring absolute precision or a perfectmatch (e.g., within +/−20% for quantifiable properties). The term“substantially”, unless otherwise specifically defined, means to a highdegree of approximation (e.g., within +/−10% for quantifiableproperties) but again without requiring absolute precision or a perfectmatch. Terms such as same, equal, uniform, constant, strictly, and thelike, are understood to be within the usual tolerances or measuringerror applicable to the particular circumstance rather than requiringabsolute precision or a perfect match.

In a first aspect, the present disclosure provides a photopolymerizablecomposition. The photopolymerizable composition comprises a (e.g.,miscible) blend of:

-   -   a. 30 to 70 wt. %, inclusive, of at least one urethane        component;    -   b. 25 to 70 wt. %, inclusive, of at least one monofunctional        reactive diluent, wherein the at least one monofunctional        reactive diluent comprises at least one monofunctional reactive        diluent having a T_(g) of up to but not including 25 degrees        Celsius;    -   c. optionally at least one multifunctional reactive diluent in        an amount of 1 to 30 wt. %, inclusive, if present, based on the        total weight of the photopolymerizable composition;    -   d. 0.1 to 5 wt. %, inclusive, of at least one initiator; and    -   e. an optional inhibitor in an amount of 0.001 to 1 wt. %,        inclusive, if present, based on the total weight of the        photopolymerizable composition.

The components (a) through (e) are discussed in detail below.

Urethane Component

The photopolymerizable compositions of the present disclosure include atleast one urethane component. As used herein, a “urethane component”refers to a compound including one or more carbamate functionalities inthe backbone of the compound. In certain embodiments, the carbamatefunctionality is of Formula I:

—N(H)—C(O)O—  I.

Urethanes are prepared by the reaction of an isocyanate with an alcoholto form carbamate linkages. Moreover, the term “polyurethane” has beenused more generically to refer to the reaction products ofpolyisocyanates with any polyactive hydrogen compound includingpolyfunctional alcohols, amines, and mercaptans.

The at least one urethane component provides both toughness (e.g., atleast a minimum tensile strength and/or modulus) and flexibility (e.g.,at least a minimum elongation at break) to the final article. In someembodiments, in addition to the urethane functionality, the urethanecomponent further comprises one or more functional groups selected fromhydroxyl groups, carboxyl groups, amino groups, and siloxane groups.These functional groups can be reactive with other components of thephotopolymerizable composition during polymerization. The at least oneurethane component often comprises a urethane (meth)acrylate, a urethaneacrylamide, or combinations thereof, and wherein the at least oneurethane component comprises a linking group selected from alkyl,polyalkylene, polyalkylene oxide, aryl, polycarbonate, polyester,polyamide, and combinations thereof. As used herein, “linking group”refers to a functional group that connects two or more urethane groups.The linking group may be divalent, trivalent, or tetravalent. In selectembodiments, the at least one urethane component comprises a urethane(meth)acrylate comprising a polyalkylene oxide linking group, apolyamide linking group, or combinations thereof.

For example, the polymerizable component can include polyfunctionalurethane acrylates or urethane methacrylates. These urethane(meth)acrylates are known to the person skilled in the art and can beprepared in a known manner by, for example, reacting ahydroxyl-terminated polyurethane with acrylic acid, methacrylic acid, orisocyanatoethyl methacrylate, or by reacting an isocyanate-terminatedprepolymer with hydroxyalkyl (meth)acrylates to give the urethane(meth)acrylate. Suitable processes are disclosed, inter alia, in U.S.Pat. No. 8,329,776 (Hecht et al.) and U.S. Pat. No. 9,295,617 (Cub etal.). Suitable urethane methacrylates can include aliphatic urethanemethacrylates, aliphatic polyester urethane methacrylates, and aliphaticpolyester triurethane acrylates.

Typically, the urethane component comprises a number average molecularweight (Mn) of 200 grams per mole to 5,000 grams per mole. The numberaverage molecular weight may be measured by matrix assisted laserdeposition ionization mass spectrometry (MALDI). The “urethanecomponent” as used herein optionally includes each of a “high Mnurethane component” and a “low Mn urethane component”. The high Mnurethane component encompasses compounds including one or more urethanefunctionalities in the backbone of the compound and that have a numberaverage molecular weight of 1,000 grams per mole (g/mol) or greater,with the proviso that all branches off the backbone of the compound, ifpresent, have a Mn of no more than 200 g/mol. Stated another way, thehigh Mn urethane component typically has a Mn of 1,000 g/mol or greater,1,100 g/mol or greater, 1,200 g/mol or greater, 1,300 g/mol or greater,1,400 g/mol or greater, 1,500 g/mol or greater, 1,600 g/mol or greater,1,700 g/mol or greater, 1,800 g/mol or greater, 2,000 g/mol or greater,2,250 g/mol or greater, 2,500 g/mol or greater, 2,750 g/mol or greater,3,000 g/mol or greater, 3,250 g/mol or greater, 3,500 g/mol or greater,3,7500 g/mol or greater, or even 4,000 g/mol or greater; and 5,000 g/molor less, 4,800 g/mol or less, 4,600 g/mol or less, 4,400 g/mol or less,4,100 g/mol or less, 3,900 g/mol or less, 3,700 g/mol or less, 3,400g/mol or less, 3,100 g/mol or less, 2,900 g/mol or less, 2,700 g/mol orless, 2,400 g/mol or less, or 2,200 g/mol or less, or even 1,900 g/molor less.

The low Mn urethane component encompasses compounds including one ormore urethane functionalities in the backbone of the compound and thathave either 1) a number average molecular weight of 100 g/mol or greaterand up to but not including 1,000 g/mol, or 2) a number averagemolecular weight of 100 g/mol or greater and 2,000 g/mol or less, withthe proviso that a number average molecular weight of any one or morelinear portions between two reactive groups and/or branches is up to butnot including 1,000 g/mol. For instance, a branched urethane componentcan have a total Mn of greater than 1,000 g/mol but still be a low Mnurethane component due to having a linear segment between two branchingpoints with a Mn of less than 1,000 g/mol. Stated another way, the 1)category of low Mn urethane components typically have a Mn of 100 g/molor greater, 150 g/mol or greater, 200 g/mol or greater, 250 g/mol orgreater, 300 g/mol or greater, 350 g/mol or greater, 400 g/mol orgreater, 450 g/mol or greater, 500 g/mol or greater, 550 g/mol orgreater, 600 g/mol or greater, 650 g/mol or greater, 700 g/mol orgreater, 750 g/mol or greater, or 800 g/mol or greater; and up to butnot including 1,000 g/mol, 975 g/mol or less, 925 g/mol or less, 875g/mol or less, 825 g/mol or less, 775 g/mol or less, 725 g/mol or less,675 g/mol or less, 625 g/mol or less, 575 g/mol or less, 525 g/mol orless, 475 g/mol or less, or 425 g/mol or less, or even 375 g/mol orless. The 2) category of low Mn urethane components typically have a Mnof 200 g/mol or greater, 250 g/mol or greater, 300 g/mol or greater, 350g/mol or greater, 400 g/mol or greater, 450 g/mol or greater, 500 g/molor greater, 550 g/mol or greater, 600 g/mol or greater, 650 g/mol orgreater, 700 g/mol or greater, 750 g/mol or greater, or 800 g/mol orgreater; and 1,500 g/mol or less, 1,400 g/mol or less, 1,300 g/mol orless, 1,200 g/mol or less, 1,100 g/mol or less, 1,000 g/mol or less, 975g/mol or less, 925 g/mol or less, 875 g/mol or less, 825 g/mol or less,775 g/mol or less, 725 g/mol or less, 675 g/mol or less, 625 g/mol orless, 575 g/mol or less, 525 g/mol or less, 475 g/mol or less, or 425g/mol or less, or even 375 g/mol or less. Each of the foregoing secondcategory of low Mn urethane components includes the proviso that anumber average molecular weight of any one or more linear portionsbetween two reactive groups and/or branches is up to but not including1,000 g/mol, 950 g/mol or less, 900 g/mol or less, 850 g/mol or less,800 g/mol or less, or 750 g/mol or less; and a number average molecularweight of any one or more linear portions between two reactive groupsand/or branches is 100 g/mol or greater, 200 g/mol or greater, 250 g/molor greater, 300 g/mol or greater, 350 g/mol or greater, 400 g/mol orgreater, 450 g/mol or greater, or 500 g/mol or greater.

The use of high Mn urethane components having a number average molecularweight of 1,000 g/mol or greater tend to provide a final article havingat least a certain desirable minimum elongation at break (e.g., 25% orgreater). Eighty percent by weight or greater of the at least oneurethane component is provided by one or more high Mn (e.g., long chain)urethane components. More particularly, in embodiment where a lowmolecular weight urethane component is present, typical ratios of thehigh number average molecular weight urethane component to the lownumber average molecular weight urethane component range from 95:5 highMn urethane component to low Mn urethane component to 80:20 high Mnurethane component to low Mn urethane component. Stated another way,photopolymerizable compositions according to at least certain aspects ofthe disclosure include 80 wt. % or more of the total urethane componentas a high Mn urethane component, 85 wt. % or more, 87 wt. % or more, 90wt. % or more, 92 wt. % or more, 95 wt. % or more, or even 97 wt. % ormore of the total urethane component as a high Mn urethane component;and 100% or less of the total urethane component as a high Mn urethanecomponent, 98 wt. % or less, 96 wt. % or less, 94 wt. % or less, 91 wt.% or less, 89 wt. % or less, or 86 wt. % or less of the total urethanecomponent as a high Mn urethane component. Similarly, photopolymerizablecompositions according to at least certain aspects of the disclosure caninclude 2 wt. % or more of the total urethane component as a low Mnurethane component, 4 wt. % or more, 5 wt. % or more, 8 wt. % or more,10 wt. % or more, 12 wt. % or more, 15 wt. % or more, or even 17 wt. %or more of the total urethane component as a low Mn urethane component;and 20 wt. % or less of the total urethane component as a low Mnurethane component, 18 wt. % or less, 16 wt. % or less, 14 wt. % orless, 11 wt. % or less, 9 wt. % or less, 7 wt. % or less, 6 wt. % orless, or 3 wt. % or less of the total urethane component as a low Mnurethane component.

According to certain embodiments, at least one urethane componentcomprises at least one (meth)acrylate component having a urethanemoiety, which may help to improve physical properties of the curedcomposition like flexural strength and/or elongation at break. Such aurethane component can be characterized by the following features aloneor in combination:

-   -   a) comprising at least 2 or 3 or 4 (meth)acrylate moieties;    -   b) number average molecular weight (Mn): from 1,000 to 5,000        g/mol or from 1,000 to 2000 g/mol;    -   c) comprising a C1 to C20 linear or branched alkyl moiety to        which the (meth)acrylate moieties are attached through urethane        moieties;    -   d) viscosity: from 0.1 to 100 Pa·s or 1 to 50 Pa·s at 23° C.

A combination of the features a) and b) or b) and c) or a) and d) cansometimes be preferred.

Urethane (meth)acrylates may be obtained by a number of processes knownto the skilled person. The urethane(meth)acrylates are typicallyobtained by reacting an NCO-terminated compound with a suitablemonofunctional (meth)acrylate monomer such as hydroxyethyl acrylate,hydroxyethyl methacrylate, hydroxypropylmethacrylate, preferablyhydroxyethyl- and hydroxypropylmethacrylate. For example, apolyisocyanate and a polyol may be reacted to form anisocyanate-terminated urethane prepolymer that is subsequently reactedwith a (meth)acrylate such as 2-hydroxy ethyl(meth)acrylate. These typesof reactions may be conducted at room temperature or higher temperature,optionally in the presence of catalysts such as tin catalysts, tertiaryamines and the like.

Polyisocyanates which can be employed to form isocyanate-functionalurethane prepolymers can be any organic isocyanate having at least twofree isocyanate groups. Included are aliphatic cycloaliphatic, aromaticand araliphatic isocyanates. Any of the known polyisocyanates such asalkyl and alkylene polyisocyanates, cycloalkyl and cycloalkylenepolyisocyanates, and combinations such as alkylene and cycloalkylenepolyisocyanates can be employed. Preferably, diisocyanates having theformula X(NCO)₂ can be used, with X representing an aliphatichydrocarbon radical with 2 to 12 C atoms, a cycloaliphatic hydrocarbonradical with 5 to 18 C atoms, an aromatic hydrocarbon radical with 6 to16 C atoms and/or an aliphatic hydrocarbon radical with 7 to 15 C atoms.

Examples of suitable polyisocyanates include2,2,4-trimethylhexamethylene-1,6-diisocyanate,hexamethylene-1,6-diisocyanate (HDI), cyclohexyl-1,4-diisocyanate,4,4′-methylene-bis(cyclohexyl isocyanate),1,1′-methylenebis(4-isocyanato) cyclohexane, isophorone diisocyanate,4,4′-methylene diphenyl diisocyanate, 1,4-tetramethylene diisocycanate,meta- and para-tetra methylxylene diisocycanate, 1,4-phenylenediisocycanate, 2,6- and 2,4-toluene diisocycanate, 1,5-naphthylenediisocycanate, 2,4′ and 4,4′-diphenylmethane diisocycanate and mixturesthereof.

It is also possible to use higher-functional polyisocyanates known frompolyurethane chemistry or else modified polyisocyanates, for examplecontaining carbodiimide groups, allophanate groups, isocyanurate groupsand/or biuret groups. Particularly preferred isocyanates are isophoronediisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate andhigher-functional polyisocyanates with isocyanurate structure.

The isocyanate terminated urethane compound is capped with a(meth)acrylate to produce a urethane(meth)acrylate compound. In general,any (meth)acrylate-type capping agent having a terminal hydroxyl groupand also having an acrylic or methacrylic moiety can be employed, withthe methacrylic moiety being preferred. Examples of suitable cappingagents include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, glycerol di(meth)acrylate and/or trimethylolpropanedi(meth)acrylate. Particularly preferred are 2-hydroxyethyl methacrylate(HEMA) and/or 2-hydroxyethyl acrylate (HEA).

The equivalence ratio of isocyanate groups to compounds reactivevis-á-vis isocyanate groups is 1.1:1 to 8:1, preferably 1.5:1 to 4:1.

The isocyanate polyaddition reaction can take place in the presence ofcatalysts known from polyurethane chemistry, for example organotincompounds such as dibutyltin dilaurate or amine catalysts such asdiazabicyclo[2.2.2]octane. Furthermore, the synthesis can take placeboth in the melt or in a suitable solvent which can be added before orduring the prepolymer preparation. Suitable solvents are for exampleacetone, 2-butanone, tetrahydrofurane, dioxane, dimethylformamide,N-methyl-2-pyrrolidone (NMP), ethyl acetate, alkyl ethers of ethyleneand propylene glycol and aromatic hydrocarbons. The use of ethyl acetateas solvent is particularly preferred.

According to select embodiments the urethane dimethacrylate of thefollowing Formulas II and III are preferred:

wherein n=9 or 10;

Examples of commercially available urethane components include thoseavailable under the trade designations of EXOTHANE 108 (e.g., includingthe structure of Formula II), EXOTHANE 8, and EXOTHANE 10 (e.g.,including the structure of Formula III) from Esstech Inc, and DESMA from3M Company. DESMA is described in, e.g., paragraph [0135] and Table 3 ofEP2167013B1 (Hecht et al.).

In certain embodiments, a urethane component (e.g., an oligomer or apolymer) may be prepared including one or more pendant groups attachedto the urethane backbone. Preferably, at least one pendent groupcomprises a photoinitiator. For instance, a photoinitiator-containingethyl acrylate compound (PIEA) has been prepared via the below reactionscheme:

The reaction is described in detail in the Examples below. Next, thePIEA can be reacted with one or more monomers and a thermal initiator insolution, such as per the below reaction scheme:

This reaction is also described in detail in the Examples below. Suchphotoinitiator-carrying urethane components may be included inphotopolymerizable compositions of at least certain embodiments of thepresent disclosure. An advantage to providing the photoinitiatorattached to the urethane component is that the location ofpolymerization at the urethane backbone can be preselected.

The urethane component is included in the photopolymerizable compositionin an amount of 50 to 90 wt. %, inclusive, based on the total weight ofthe photopolymerizable composition, such as 50 to 70 wt. %, inclusive.Typically, the urethane component is included in the photopolymerizablecomposition in an amount of 50 wt. % or more, 52 wt. % or more, 55 wt. %or more, 57 wt. % or more, 60 wt. % or more, 61 wt. % or more, 62 wt. %or more, 63 wt. % or more, 64 wt. % or more, 65 wt. % or more, 70 wt. %or more, or 72 wt. % or more; and 90 wt. % or less, 87 wt. % or less, 85wt. % or less, 80 wt. % or less, 77 wt. % or less, or 75 wt. % or less,based on the total weight of the photopolymerizable composition.

Reactive Diluent

The photopolymerizable compositions of the present disclosure include atleast one monofunctional reactive diluent. A “reactive diluent,” forreference purposes herein, is a component that contains at least onefree radically reactive group (e.g., an ethylenically-unsaturated group)that can co-react with the at least one urethane component (e.g., iscapable of undergoing addition polymerization). The reactive diluent hasa smaller molecular weight than at least one (e.g., high Mn) urethanecomponent, often less than 400 grams per mole, and does not contain anyurethane functional groups (e.g., is free of any urethane functionalgroups).

The reactive diluent comprises at least one monofunctional reactivediluent having a T_(g) of up to but not including 25° C., 20° C., 15°C., or 10° C. As defined above, it is to be understood that the T_(g) isof a homopolymer of the monofunctional reactive diluent. Statementsthroughout this disclosure regarding T_(g) of a material, for instance,a monomer or oligomer, are to be understood to be shorthand for theT_(g) of a homopolymer of that material (e.g., that monomer oroligomer). Thus, stated another way, the reactive diluent comprises atleast one monofunctional reactive diluent whose homopolymer has a T_(g)of up to but not including 25° C., 20° C., 15° C., or 10° C. The T_(g)may be 24° C., 23° C., 22° C., 21° C., 20° C., 18° C., 16° C., 14° C.,12° C., 10° C., or 8° C. The inclusion of a low T_(g) monofunctionalreactive diluent tends to lower the T_(g) of a reaction product of thephotopolymerizable composition.

In some embodiments, the at least one monofunctional reactive diluentfurther comprises a second monofunctional reactive diluent, wherein (ahomopolymer of) the second monofunctional reactive diluent has a T_(g)of 25° C. or greater, 30° C. or greater, 35° C. or greater, or 40° C. orgreater. The T_(g) may be 80° C. or less, 75° C. or less, 70° C. orless, 65° C. or less, 60° C. or less, 55° C. or less, 50° C. or less, or45° C. or less. It has been unexpectedly found that a balance ofphysical properties (e.g., strength and elongation at break) can beobtained in a polymerized article when including both a monofunctionalreactive diluent having a T_(g) of less than 25° C. and a monofunctionalreactive diluent having a T_(g) of 25° C. or greater, in certainphotopolymerizable compositions according to the present disclosure.

In some embodiments, the monofunctional reactive diluent furthercomprises a third monofunctional reactive diluent, plus optionally afourth monofunctional reactive diluent. In an embodiment, the at leastone monofunctional reactive diluent comprises one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius and two monofunctional reactive diluents having a T_(g) of 25degrees Celsius or greater. In an alternative embodiment, the at leastone monofunctional reactive diluent comprises two monofunctionalreactive diluents having a T_(g) of up to but not including 25 degreesCelsius and one monofunctional reactive diluent having a T_(g) of 25degrees Celsius or greater.

In select embodiments, the (at least one) monofunctional reactivediluent comprises a (meth)acrylate, an alkyl (meth)acrylate, a phenoxy(meth)acrylate, a hydroxy alkyl (meth)acrylate, or a combinationthereof. In some preferred embodiments, the monofunctional reactivediluent comprises phenoxy ethyl methacrylate, such as in an amount of 20to 80 wt. % of the total amount of the total monofunctional reactivediluent content.

In certain embodiments, the monofunctional reactive diluent comprises an(e.g., amphiphilic) monofunctional reactive diluent. exhibiting ahydrophilic-lipophilic balance (HLB) value of less than 10. Amphiphiliccompounds can be characterized by various methodology. One commoncharacterization method, as known in the art, is thehydrophilic-lipophilic balance (“HLB”). Although various methods havebeen described for determining the HLB of a compound, as used herein,HLB refers to the value obtained by the Griffin's method (See Griffin WC: “Calculation of HLB Values of Non-Ionic Surfactants,” Journal of theSociety of Cosmetic Chemists 5 (1954): 259). The computations wereconducted utilizing the software program Molecular Modeling Pro Plusfrom Norgwyn Montgomery Software, Inc. (North Wales, Pa.). According toGriffin's method: HLB=20*Mh/M where Mh is the molecular mass of thehydrophilic portion of the molecule, and M is the molecular mass of thewhole molecule. This computation provides a numerical result on a scaleof 0 to 20, wherein “0” is highly lipophilic. Preferably, an amphiphilicmonofunctional reactive diluent useful for at least certain embodimentsof the photopolymerizable compositions described herein exhibits ahydrophilic-lipophilic balance (HLB) value of less than 10, 9 or less, 8or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 orless; and 0.1 or more, 0.25 or more, 0.5 or more, 0.75 or more, or 1 ormore.

Suitable free-radically polymerizable monofunctional diluents includephenoxy ethyl(meth)acrylate, phenoxy-2-methylethyl(meth)acrylate,phenoxyethoxyethyl(meth)acrylate,3-hydroxy-2-hydroxypropyl(meth)acrylate, benzyl(meth)acrylate,phenylthio ethyl acrylate, 2-naphthylthio ethyl acrylate, 1-naphthylthioethyl acrylate, 2,4,6-tribromophenoxy ethyl acrylate, 2,4-dibromophenoxyethyl acrylate, 2-bromophenoxy ethyl acrylate, 1-naphthyloxy ethylacrylate, 2-naphthyloxy ethyl acrylate, phenoxy 2-methylethyl acrylate,phenoxyethoxyethyl acrylate, 3-phenoxy-2-hydroxy propyl acrylate,2,4-dibromo-6-sec-butylphenyl acrylate, 2,4-dibromo-6-isopropylphenyl(meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, alkoxylated tetrahydrofurfurylacrylate, ethoxylated nonyl phenol (meth)acrylate, alkoxylated lauryl(meth)acrylate, alkoxylated phenol (meth)acrylate, stearyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, lauryl(meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate,octadecyl (meth)acrylate, tridecyl (meth)acrylate, ethoxylated (4) nonylphenol (meth)acrylate, caprolactone (meth)acrylate, cyclictrimethylolpropane formal (meth)acrylate, 3,3,5-trimethylcyclohexyl(meth)acrylate, dicyclopentadienyl (meth)acrylate, isobutyl(meth)acrylate, n-butyl (meth)acrylate, ethyl hexyl (meth)acrylate,isobornyl (meth)acrylate, and 2,4,6-tribromophenyl (meth)acrylate.

In some embodiments, a monofunctional reactive diluent acts as acompatibilizer, which improves the interfacial adhesion between twootherwise immiscible material phases (e.g., the urethane component andone or more other reactive diluent(s)). The amount of compatibilizerused is relative to the amount of the urethane component. Typically, amonofunctional reactive diluent compatibilizer is present in aphotopolymerizable composition in an amount of 30 wt. % or greater ofthe amount of the at least one urethane component, or 35 wt. % orgreater, or 40 wt. % or greater, of the amount of the at least oneurethane component. In certain embodiments of the photopolymerizablecomposition, the presence of a compatibilizer enables the composition tobe a (miscible) blend instead of more than one substantially separatephase. Some monofunctional reactive diluents that can act ascompatibilizers include for instance phenoxy ethyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, and n-vinyl pyrrolidone.

Suitable free-radically polymerizable multifunctional reactant diluentsinclude di-, tri-, or other poly-acrylates and methacrylates such asglycerol diacrylate, ethoxylated bisphenol A dimethacrylate(D-zethacrylate), tetraethylene glycol dimethacrylate (TEGDMA),polyethyleneglycol dimethacrylate (PEGDMA), glycerol triacrylate,ethyleneglycol diacrylate, diethyleneglycol diacrylate,triethyleneglycol dimethacrylate, 1,3-propanediol diacrylate,1,3-propanediol dimethacrylate, trimethylolpropane triacrylate,1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate,pentaerythritol triacrylate, pentaerythritol tetraacrylate,pentaerythritol tetramethacrylate, sorbitol hexacrylate,bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, andtrishydroxyethyl-isocyanurate trimethacrylate; bis-acrylates ofpolyesters (e.g., methacrylate-terminated polyesters); the bis-acrylatesand bis-methacrylates of polyethylene glycols of molecular weight200-500, copolymerizable mixtures of acrylated monomers such as those inU.S. Pat. No. 4,652,274 (Boettcher et al.), and acrylated oligomers suchas those of U.S. Pat. No. 4,642,126 (Zador et al.); polyfunctional(meth)acrylates comprising urea or amide groups, such as those ofEP2008636 (Hecht et al.).

The reactive diluent can comprise one or more poly(meth)acrylates, forexample, di-, tri-, tetra- or pentafunctional monomeric or oligomericaliphatic, cycloaliphatic or aromatic acrylates or methacrylates.

Examples of suitable aliphatic poly(meth)acrylates having more than two(meth)acrylate groups in their molecules are the triacrylates andtrimethacrylates of hexane-2,4,6-triol; glycerol or1,1,1-trimethylolpropane; ethoxylated or propoxylated glycerol or1,1,1-trimethylolpropane; and the hydroxyl-containing tri(meth)acrylateswhich are obtained by reacting triepoxide compounds, for example thetriglycidyl ethers of said triols, with (meth)acrylic acid. It is alsopossible to use, for example, pentaerythritol tetraacrylate,bistrimethylolpropane tetraacrylate, pentaerythritolmonohydroxytriacrylate or -methacrylate, or dipentaerythritolmonohydroxypentaacrylate or—methacrylate.

Another suitable class of free radical polymerizable compounds includesaromatic di(meth)acrylate compounds and trifunctional or higherfunctionality (meth)acrylate compound. Trifunctional or higherfunctionality meth(acrylates) can be tri-, tetra- or pentafunctionalmonomeric or oligomeric aliphatic, cycloaliphatic or aromatic acrylatesor methacrylates.

Examples of suitable aliphatic tri-, tetra- and pentafunctional(meth)acrylates are the triacrylates and trimethacrylates ofhexane-2,4,6-triol; glycerol or 1,1,1-trimethylolpropane; ethoxylated orpropoxylated glycerol or 1,1,1-trimethylolpropane; and thehydroxyl-containing tri(meth)acrylates which are obtained by reactingtriepoxide compounds, for example the triglycidyl ethers of said triols,with (meth)acrylic acid. It is also possible to use, for example,pentaerythritol tetraacrylate, bistrimethylolpropane tetraacrylate,pentaerythritol monohydroxytriacrylate or -methacrylate, ordipentaerythritol monohydroxypentaacrylate or—methacrylate. In someembodiments, tri(meth)acrylates comprise 1,1-trimethylolpropanetriacrylate or methacrylate, ethoxylated or propoxylated1,1,1-trimethylolpropanetriacrylate or methacrylate, ethoxylated orpropoxylated glycerol triacrylate, pentaerythritol monohydroxytriacrylate or methacrylate, or tris(2-hydroxy ethyl) isocyanuratetriacrylate. Further examples of suitable aromatic tri(meth)acrylatesare the reaction products of triglycidyl ethers of trihydroxy benzeneand phenol or cresol novolaks containing three hydroxyl groups, with(meth)acrylic acid.

In some cases, a reactive diluent comprises diacrylate and/ordimethacrylate esters of aliphatic, cycloaliphatic or aromatic diols,including 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol,dodecane diol, diethylene glycol, triethylene glycol, tetraethyleneglycol, polyethylene glycol, tripropylene glycol, ethoxylated orpropoxylated neopentyl glycol, 1,4-dihydroxymethylcyclohexane,2,2-bis(4-hydroxycyclohexyl)propane or bis(4-hydroxycyclohexyl)methane,hydroquinone, 4,4′-dihydroxybiphenyl, bisphenol A, bisphenol F,bisphenol S, ethoxylated or propoxylated bisphenol A, ethoxylated orpropoxylated bisphenol F or ethoxylated or propoxylated bisphenol S. Insome cases, a reactive diluent described herein comprises one or morehigher functional acrylates or methacrylates such as dipentaerythritolmonohydroxy pentaacrylate or bis(trimethylolpropane)tetraacrylate.

In some embodiment comprising a multifunctional reactive diluent, one ormore multifunctional reactive diluents are present in an amount of 1 to30 wt. %, inclusive, such as 5 to 20 wt. %, based on the total weight ofthe photopolymerizable composition. Stated another way, at least onemultifunctional reactive diluent may be present in an amount of 1 wt. %or more, 3 wt. % or more, 5 wt. % or more, 10 wt. % or more, or 15 wt. %or more; and 30 wt. % or less, 25 wt. % or less, 20 wt. % or less, or 17wt. % or less, based on the total weight of the photopolymerizablecomposition.

In certain other embodiments, the photopolymerizable compositionconsists essentially of monofunctional components or is free ofmultifunctional components. This means that the photopolymerizablecomposition contains 2 wt. % or less of multifunctional components. Itwas unexpectedly discovered that a significant amount of themonofunctional reactive diluents are incorporated into the reactionproduct of the photopolymerizable composition duringphotopolymerization. This means that a relatively small amount ofunreacted monofunctional reactive diluent remains in the reactionproduct and could be extracted from the cured composition, particularlyafter subjection of the cured composition to a post-cure step. Incertain embodiments, 10% or less of unreacted monofunctional reactivediluent is present in a cured or post-cured article.

In select embodiments, two or more reactive diluents are prepolymerizedsuch that up to 10%, up to 15%, or up to 20% of the functional groups ofthe reactive diluents are reacted prior to inclusion in thephotopolymerizable composition. The prepolymerization is typicallyperformed via initiation with a small amount of photoinitiator added tothe reactive diluents. One representative prepolymerization process isdescribed in detail in the Examples below. An advantage ofprepolymerizing a portion of the reactive diluent(s) is the formation ofa semi-interpenetrative polymer network. Also, the prepolymerizationtends to assist in producing higher molecular weight chains in thereaction product of the photopolymerizable composition as compared tothe same composition that is not prepolymerized.

In certain embodiments, the at least one reactive diluent has amolecular weight of 400 grams per mole or less, 375 g/mol or less, 350g/mol or less, 325 g/mol or less, 300 g/mol or less, 275 g/mol or less,225 g/mol or less, or 200 g/mol or less. Including one or more reactivediluents with such molecular weights can assist in providing aphotopolymerizable composition that has a sufficiently low viscosity foruse with vat polymerization methods. In certain embodiments, the atleast one reactive diluent comprises a molecular weight of 200 g/mol to400 g/mol, inclusive.

The reactive diluent is included in the photopolymerizable compositionin an amount of 25 to 70 wt. %, inclusive, based on the total weight ofthe photopolymerizable composition, such as 30 to 50 wt. %, inclusive.Typically, the reactive diluent is included in the photopolymerizablecomposition in an amount of 25 wt. % or more, 30 wt. % or more, or 35wt. % or more; and 70 wt. % or less, 65 wt. % or less, 60 wt. % or less,55 wt. % or less, 50 wt. % or less, 45 wt. % or less, or 40 wt. % orless, based on the total weight of the photopolymerizable composition.

Additives

Photopolymerizable compositions described herein, in some instances,further comprise one or more additives, such as one or more additivesselected from the group consisting of photoinitiators, thermalinitiators, inhibitors, stabilizing agents, sensitizers, absorptionmodifiers, fillers and combinations thereof. For example, thephotopolymerizable composition further comprises one or morephotoinitiators, for instance two photoinitiators. Suitable exemplaryphotoinitiators are those available under the trade designationsIRGACURE and DAROCUR from BASF (Ludwigshafen, Germany) and include1-hydroxycyclohexyl phenyl ketone (IRGACURE 184),2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651), bis(2,4,6trimethylbenzoyl)phenylphosphineoxide (IRGACURE 819),1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone(IRGACURE 369),2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE907), Oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone]ESACURE ONE (Lamberti S. p. A., Gallarate, Italy),2-hydroxy-2-methyl-1-phenyl propan-1-one (DAROCUR 1173),2,4,6-trimethylbenzoyldiphenylphosphine oxide (IRGACURE TPO), and2,4,6-trimethylbenzoylphenyl phosphinate (IRGACURE TPO-L). Additionalsuitable photoinitiators include for example and without limitation,benzyl dimethyl ketal, 2-methyl-2-hydroxypropiophenone, benzoin methylether, benzoin isopropyl ether, anisoin methyl ether, aromatic sulfonylchlorides, photoactive oximes, and combinations thereof.

A photoinitiator can be present in a photopolymerizable compositiondescribed herein in any amount according to the particular constraintsof the additive manufacturing process. In some embodiments, aphotoinitiator is present in a photopolymerizable composition in anamount of up to about 5% by weight, based on the total weight of thephotopolymerizable composition. In some cases, a photoinitiator ispresent in an amount of about 0.1-5% by weight, based on the totalweight of the photopolymerizable composition.

A thermal initiator can be present in a photopolymerizable compositiondescribed herein in any amount according to the particular constraintsof the additive manufacturing process. In some embodiments, a thermalinitiator is present in a photopolymerizable composition in an amount ofup to about 5% by weight, based on the total weight of thephotopolymerizable composition. In some cases, a thermal initiator ispresent in an amount of about 0.1-5% by weight, based on the totalweight of the photopolymerizable composition. Suitable thermalinitiators include for instance and without limitation, peroxides suchas benzoyl peroxide, dibenzoyl peroxide, dilauryl peroxide, cyclohexaneperoxide, methyl ethyl ketone peroxide, hydroperoxides, e.g., tert-butylhydroperoxide and cumene hydroperoxide, dicyclohexyl peroxydicarbonate,2,2,-azo-bis(isobutyronitrile), and t-butyl perbenzoate. Examples ofcommercially available thermal initiators include initiators availablefrom DuPont Specialty Chemical (Wilmington, Del.) under the VAZO tradedesignation including VAZO 67 (2,2′-azo-bis(2-methybutyronitrile)) VAZO64 (2,2′-azo-bis(isobutyronitrile)) and VAZO 52(2,2′-azo-bis(2,2-dimethyvaleronitrile)), and LUCIDOL 70 from ElfAtochem North America, Philadelphia, Pa.

In certain aspects, the use of more than one initiator assists inincreasing the percentage of reactive diluent that gets incorporatedinto the reaction product and thus decreasing the percentage of thereactive diluent that remains uncured. Reaction of monofunctionalreactive diluent(s) in particular is desirable to minimize the presenceof unreacted diluent in the product following polymerization.

In addition, a photopolymerizable material composition described hereincan further comprise one or more sensitizers to increase theeffectiveness of one or more photoinitiators that may also be present.In some embodiments, a sensitizer comprises isopropylthioxanthone (ITX)or 2-chlorothioxanthone (CTX). Other sensitizers may also be used. Ifused in the photopolymerizable composition, a sensitizer can be presentin an amount ranging of about 0.01% by weight or about 1% by weight,based on the total weight of the photopolymerizable composition.

A photopolymerizable composition described herein optionally alsocomprises one or more polymerization inhibitors or stabilizing agents. Apolymerization inhibitor is often included in a photopolymerizablecomposition to provide additional thermal stability to the composition.A stabilizing agent, in some instances, comprises one or moreanti-oxidants. Any anti-oxidant not inconsistent with the objectives ofthe present disclosure may be used. In some embodiments, for example,suitable anti-oxidants include various aryl compounds, includingbutylated hydroxytoluene (BHT), which can also be used as apolymerization inhibitor in embodiments described herein. In addition toor as an alternative, a polymerization inhibitor comprisesmethoxyhydroquinone (MEHQ).

In some embodiments, a polymerization inhibitor, if used, is present inan amount of about 0.001-2% by weight, 0.001 to 1% by weight, or 0.01-1%by weight, based on the total weight of the photopolymerizablecomposition. Further, if used, a stabilizing agent is present in aphotopolymerizable composition described herein in an amount of about0.1-5% by weight, about 0.5-4% by weight, or about 1-3% by weight, basedon the total weight of the photopolymerizable composition.

A photopolymerizable composition as described herein can also compriseone or more absorption modifiers (e.g., dyes, optical brighteners,pigments, particulate fillers, etc.) to control the penetration depth ofactinic radiation. One particularly suitable absorption modifier isTinopal OB, a benzoxazole,2,2′-(2,5-thiophenediyl)bis[5-(1,1-dimethylethyl)], available from BASFCorporation, Florham Park, N.J. The absorption modifier, if used, can bepresent in an amount of about 0.001-5% by weight, about 0.01-1% byweight, about 0.1-3% by weight, or about 0.1-1% by weight, based on thetotal weight of the photopolymerizable composition.

Photopolymerizable compositions may include fillers, includingnano-scale fillers. Examples of suitable fillers are naturally occurringor synthetic materials including, but not limited to: silica (SiO₂(e.g., quartz)); alumina (Al₂O₃), zirconia, nitrides (e.g., siliconnitride); glasses and fillers derived from, for example, Zr, Sr, Ce, Sb,Sn, Ba, Zn, and Al; feldspar; borosilicate glass; kaolin (china clay);talc; zirconia; titania; and submicron silica particles (e.g., pyrogenicsilicas such as those available under the trade designations AEROSIL,including “OX 50,” “130,” “150” and “200” silicas from Degussa Corp.,Akron, Ohio and CAB-O-SIL M5 and TS-720 silica from Cabot Corp.,Tuscola, Ill.). Organic fillers made from polymeric materials are alsopossible, such as those disclosed in International Publication No.WO09/045752 (Kalgutkar et al.).

In certain embodiments, the filler comprises surface modifiednanoparticles. Generally, “surface modified nanoparticles” comprisesurface treatment agents attached to the surface of a core. In someembodiments, the core is substantially spherical. In some embodiments,the core is at least partially or substantially crystalline. In someembodiments, the particles are substantially non-agglomerated. In someembodiments, the particles are substantially non-aggregated in contrastto, for example, fumed or pyrogenic silica. Generally, surface treatmentagents for silica nanoparticles are organic species having a firstfunctional group capable of covalently chemically attaching to thesurface of a nanoparticle, wherein the attached surface treatment agentalters one or more properties of the nanoparticle. In some embodiments,surface treatment agents have no more than three functional groups forattaching to the core. In some embodiments, the surface treatment agentshave a low molecular weight, e.g., a weight average molecular weightless than 1000 gm/mole.

In some embodiments, the surface-modified nanoparticles are reactive;that is, at least one of the surface treatment agents used to surfacemodify the nanoparticles of the present disclosure may include a secondfunctional group capable of reacting with one or more of the urethanecomponent and/or one or more of the reactive diluent(s) of thephotopolymerizable composition. For purposes of clarity, even when thenanoparticles are reactive, they are not considered to be constituentsof the resin component of the photopolymerizable composition. Surfacetreatment agents often include more than one first functional groupcapable of attaching to the surface of a nanoparticle. For example,alkoxy groups are common first functional groups that are capable ofreacting with free silanol groups on the surface of a silicananoparticle forming a covalent bond between the surface treatment agentand the silica surface. Examples of surface treatment agents havingmultiple alkoxy groups include trialkoxy alkylsilanes (e.g.,3-(trimethoxysilyl)propyl methacrylate) and trialkoxy arylsilanes (e.g.,trimethoxy phenyl silane).

The compositions may further contain fibrous reinforcement and colorantssuch as dyes, pigments, and pigment dyes. Examples of suitable fibrousreinforcement include PGA microfibrils, collagen microfibrils, andothers as described in U.S. Pat. No. 6,183,593 (Narang et al.). Examplesof suitable colorants as described in U.S. Pat. No. 5,981,621 (Clark etal.) include 1-hydroxy-4[4-methylphenylamino]-9,10-anthracenedione (FD&Cviolet No. 2); disodium salt of6-hydroxy-5[(4-sulfophenyl)oxo]-2-naphthalenesulfonic acid (FD&C YellowNo. 6);9-(o-carboxyphenyl)-6-hydroxy-2,4,5,7-tetraiodo-3H-xanthen-3-one,disodium salt, monohydrate (FD&C Red No. 3); and the like.

Discontinuous fibers are also suitable fillers, such as fiberscomprising carbon, ceramic, glass, or combinations thereof. Suitablediscontinuous fibers can have a variety of compositions, such as ceramicfibers. The ceramic fibers can be produced in continuous lengths, whichare chopped or sheared to provide the discontinuous ceramic fibers. Theceramic fibers can be produced from a variety of commercially availableceramic filaments. Examples of filaments useful in forming the ceramicfibers include the ceramic oxide fibers sold under the trademark NEXTEL(3M Company, St. Paul, Minn.). NEXTEL is a continuous filament ceramicoxide fiber having low elongation and shrinkage at operatingtemperatures, and offers good chemical resistance, low thermalconductivity, thermal shock resistance, and low porosity. Specificexamples of NEXTEL fibers include NEXTEL 312, NEXTEL 440, NEXTEL 550,NEXTEL 610 and NEXTEL 720. NEXTEL 312 and NEXTEL 440 are refractoryaluminoborosilicate that includes Al₂O₃, SiO₂ and B₂O₃. NEXTEL 550 andNEXTEL 720 are aluminosilica and NEXTEL 610 is alumina. Duringmanufacture, the NEXTEL filaments are coated with organic sizings orfinishes which serves as aids in textile processing. Sizing can includethe use of starch, oil, wax or other organic ingredients applied to thefilament strand to protect and aid handling. The sizing can be removedfrom the ceramic filaments by heat cleaning the filaments or ceramicfibers as a temperature of 700° C. for one to four hours.

The ceramic fibers can be cut, milled, or chopped so as to providerelatively uniform lengths, which can be accomplished by cuttingcontinuous filaments of the ceramic material in a mechanical shearingoperation or laser cutting operation, among other cutting operations.Given the highly controlled nature of certain cutting operations, thesize distribution of the ceramic fibers is very narrow and allow tocontrol the composite property. The length of the ceramic fiber can bedetermined, for instance, using an optical microscope (Olympus MX61,Tokyo, Japan) fit with a CCD Camera (Olympus DP72, Tokyo, Japan) andanalytic software (Olympus Stream Essentials, Tokyo, Japan). Samples maybe prepared by spreading representative samplings of the ceramic fiberon a glass slide and measuring the lengths of at least 200 ceramicfibers at 10× magnification.

Suitable fibers include for instance ceramic fibers available under thetrade name NEXTEL (available from 3M Company, St. Paul, Minn.), such asNEXTEL 312, 440, 610 and 720. One presently preferred ceramic fibercomprises polycrystalline α-Al₂O₃. Suitable alumina fibers aredescribed, for example, in U.S. Pat. No. 4,954,462 (Wood et al.) andU.S. Pat. No. 5,185,299 (Wood et al.). Exemplary alpha alumina fibersare marketed under the trade designation NEXTEL 610 (3M Company, St.Paul, Minn.). In some embodiments, the alumina fibers arepolycrystalline alpha alumina fibers and comprise, on a theoreticaloxide basis, greater than 99 percent by weight Al₂O₃ and 0.2-0.5 percentby weight SiO₂, based on the total weight of the alumina fibers. Inother embodiments, some desirable polycrystalline, alpha alumina fiberscomprise alpha alumina having an average grain size of less than onemicrometer (or even, in some embodiments, less than 0.5 micrometer). Insome embodiments, polycrystalline, alpha alumina fibers have an averagetensile strength of at least 1.6 GPa (in some embodiments, at least 2.1GPa, or even, at least 2.8 GPa). Suitable aluminosilicate fibers aredescribed, for example, in U.S. Pat. No. 4,047,965 (Karst et al).

Exemplary aluminosilicate fibers are marketed under the tradedesignations NEXTEL 440, and NEXTEL 720, by 3M Company (St. Paul,Minn.). Aluminoborosilicate fibers are described, for example, in U.S.Pat. No. 3,795,524 (Sowman). Exemplary aluminoborosilicate fibers aremarketed under the trade designation NEXTEL 312 by 3M Company. Boronnitride fibers can be made, for example, as described in U.S. Pat. No.3,429,722 (Economy) and U.S. Pat. No. 5,780,154 (Okano et al.).

Ceramic fibers can also be formed from other suitable ceramic oxidefilaments. Examples of such ceramic oxide filaments include thoseavailable from Central Glass Fiber Co., Ltd. (e.g., EFH75-01,EFH150-31). Also preferred are aluminoborosilicate glass fibers, whichcontain less than about 2% alkali or are substantially free of alkali(i.e., “E-glass” fibers). E-glass fibers are available from numerouscommercial suppliers.

Examples of useful pigments include, without limitation: white pigments,such as titanium oxide, zinc phosphate, zinc sulfide, zinc oxide andlithopone; red and red-orange pigments, such as iron oxide (maroon, red,light red), iron/chrome oxide, cadmium sulfoselenide and cadmium mercury(maroon, red, orange); ultramarine (blue, pink and violet), chrome-tin(pink) manganese (violet), cobalt (violet); orange, yellow and buffpigments such as barium titanate, cadmium sulfide (yellow), chrome(orange, yellow), molybdate (orange), zinc chromate (yellow), nickeltitanate (yellow), iron oxide (yellow), nickel tungsten titanium, zincferrite and chrome titanate; brown pigments such as iron oxide (buff,brown), manganese/antimony/titanium oxide, manganese titanate, naturalsiennas (umbers), titanium tungsten manganese; blue-green pigments, suchas chrome aluminate (blue), chrome cobalt-alumina (turquoise), iron blue(blue), manganese (blue), chrome and chrome oxide (green) and titaniumgreen; as well as black pigments, such as iron oxide black and carbonblack. Combinations of pigments are generally used to achieve thedesired color tone in the cured composition.

The use of florescent dyes and pigments can also be beneficial inenabling the printed composition to be viewed under black-light. Aparticularly useful hydrocarbon soluble fluorescing dye is2,5-bis(5-tert-butyl-2-benzoxazolyl) 1 thiophene. Fluorescing dyes, suchas rhodamine, may also be bound to cationic polymers and incorporated aspart of the resin.

If desired, the compositions of the disclosure may contain otheradditives such as indicators, accelerators, surfactants, wetting agents,antioxidants, tartaric acid, chelating agents, buffering agents, andother similar ingredients that will be apparent to those skilled in theart. Additionally, medicaments or other therapeutic substances can beoptionally added to the photopolymerizable compositions. Examplesinclude, but are not limited to, fluoride sources, whitening agents,anticaries agents (e.g., xylitol), remineralizing agents (e.g., calciumphosphate compounds and other calcium sources and phosphate sources),enzymes, breath fresheners, anesthetics, clotting agents, acidneutralizers, chemotherapeutic agents, immune response modifiers,thixotropes, polyols, anti-inflammatory agents, antimicrobial agents,antifungal agents, agents for treating xerostomia, desensitizers, andthe like, of the type often used in dental compositions.

Combinations of any of the above additives may also be employed. Theselection and amount of any one such additive can be selected by one ofskill in the art to accomplish the desired result without undueexperimentation.

Photopolymerizable compositions herein can also exhibit a variety ofdesirable properties, non-cured, cured, and as post-cured articles. Aphotopolymerizable composition, when non-cured, has a viscosity profileconsistent with the requirements and parameters of one or more additivemanufacturing devices (e.g., 3D printing systems). In some instances, aphotopolymerizable composition described herein when non-cured exhibitsa dynamic viscosity of about 0.1-1,000 Pa·s, about 0.1-100 Pa·s, orabout 1-10 Pa·s, using a TA Instruments AR-G2 magnetic bearing rheometerusing a 40 mm cone and plate measuring system at 40 degrees Celsius andat a shear rate of 0.1 1/s, when measured according to ASTM D4287, asset forth in the Example Test Method below. In some cases, aphotopolymerizable composition described herein when non-cured exhibitsa dynamic viscosity of less than about 10 Pa·s, when measured accordingto modified ASTM D4287.

Articles and Methods

In a second aspect, the present disclosure provides an article. Thearticle comprises a reaction product of a photopolymerizablecomposition, the photopolymerizable composition comprising a blend of:

-   -   a. 30 to 70 wt. %, inclusive, of at least one urethane        component;    -   b. 25 to 70 wt. %, inclusive, of at least one monofunctional        reactive diluent, wherein the at least one monofunctional        reactive diluent comprises at least one monofunctional reactive        diluent having a T_(g) of up to but not including 25 degrees        Celsius;    -   c. optionally at least one difunctional reactive diluent in an        amount of 1 to 30 wt. %, inclusive, if present, based on the        total weight of the photopolymerizable composition;    -   d. 0.1 to 5 wt. %, inclusive, of at least one initiator; and    -   e. an optional inhibitor in an amount of 0.001 to 1 wt. %,        inclusive, if present, based on the total weight of the        photopolymerizable composition.

In many embodiments, the photopolymerizable composition of the articleis vat polymerized, as discussed in detail below.

The shape of the article is not limited, and may comprise a film or ashaped integral article. For instance, a film may readily be prepared bycasting the photopolymerizable composition according to the firstaspect, then subjecting the cast composition to actinic radiation topolymerize the photopolymerizable composition. In many embodiments, thearticle comprises a shaped integral article, in which more than onevariation in dimension is provided by a single integral article. Forexample, the article can comprise one or more channels, one or moreundercuts, one or more perforations, or combinations thereof. Suchfeatures are typically not possible to provide in an integral articleusing conventional molding methods. In some embodiments, the articlecomprises a plurality of layers. In select embodiments, the articlecomprises an orthodontic article. Orthodontic articles are described infurther detail below.

In a third aspect, the present disclosure provides a method of making anarticle. The method comprises:

-   -   (a) providing a photopolymerizable composition comprising a        blend of: (i) 30 to 70 wt. %, inclusive, of at least one        urethane component; (ii) 25 to 70 wt. %, inclusive, of at least        one monofunctional reactive diluent, wherein the at least one        monofunctional reactive diluent comprises at least one        monofunctional reactive diluent having a T_(g) of up to but not        including 25 degrees Celsius; (iii) optionally at least one        difunctional reactive diluent in an amount of 1 to 30 wt. %,        inclusive, if present, based on the total weight of the        photopolymerizable composition; (iv) 0.1 to 5 wt. %, inclusive,        of at least one initiator; and (v) an optional inhibitor in an        amount of 0.001 to 1 wt. %, inclusive, if present; based on the        total weight of the photopolymerizable composition;    -   (b) selectively curing the photopolymerizable composition to        form an article; and    -   (c) optionally curing unpolymerized urethane component and/or        reactive diluent remaining after step (b).

In many embodiments, the photopolymerizable composition is cured usingactinic radiation comprising UV radiation, e-beam radiation, visibleradiation, or a combination thereof. Moreover, the method optionallyfurther comprises postcuring the article using actinic radiation orheat.

In additive manufacturing methods, the method further comprises (d)repeating steps (a) and (b) to form multiple layers and create thearticle comprising a three dimensional structure prior to step (c). Incertain embodiments, the method comprises vat polymerization of thephotopolymerizable composition. When vat polymerization is employed, theradiation may be directed through a wall of a container (e.g., a vat)holding the photopolymerizable composition, such as a side wall or abottom wall (e.g., floor).

In some embodiments, the method further comprises (e) subjecting thearticle to heating in an oven, for instance a vacuum oven. Typically,the oven is set at a temperature of 60° C. or higher. A stepwise heatingprocess is optional, such as heating at 60° C., then at 80° C., and thenat 100° C. Subjecting the article to heating is often performed to driveoff unreacted reactive diluent remaining in the article.

A photopolymerizable composition described herein in a cured state, insome embodiments, can exhibit one or more desired properties. Aphotopolymerizable composition in a “cured” state can comprise aphotopolymerizable composition that includes a polymerizable componentthat has been at least partially polymerized and/or crosslinked. Forinstance, in some instances, a cured article is at least about 10%polymerized or crosslinked or at least about 30% polymerized orcrosslinked. In some cases, a cured photopolymerizable composition is atleast about 50%, at least about 70%, at least about 80%, or at leastabout 90% polymerized or crosslinked. A cured photopolymerizablecomposition can also be between about 10% and about 99% polymerized orcrosslinked.

The conformability and durability of a cured article made from thephotopolymerizable compositions of the present disclosure can bedetermined in part by standard tensile, modulus, and/or elongationtesting. The photopolymerizable compositions can typically becharacterized by at least one of the following parameters afterhardening. Advantageously, the elongation at break is typically 25% orgreater, 27% or greater, 30% or greater, 32% or greater, 35% or greater,40% or greater, 45% or greater, 50% or greater, 55% or greater, or 60%or greater; and 200% or less, 100% or less, 90% or less, 80% or less, or70% or less. Stated another way, the elongation at break of the curedarticle can range from 25% to 200%. In some embodiments, the elongationat break is at least 30% and no greater than 100%. The ultimate tensilestrength is typically 15 MegaPascals (MPa) or greater, 20 MPA orgreater, 25 MPa or greater, or 30 MPa or greater, and is typically 80MPa or less, each as determined according to ASTM D638-10. While theurethane component has the greatest effect on the elongation at break ofan article, other components of the photopolymerizable composition alsoimpact the elongation at break, e.g., the length of a linear chain orbranch of a reactive diluent tends to be positively correlated to theelongation at break of the final article. The tensile modulus istypically 250 MPa or greater, 500 MPa or greater, 750 MPa or greater, or1,000 MPa or greater, as determined according to ASTM D638-10. Suchelongation properties can be measured, for example, by the methodsoutlined in ASTM D638-10, using test specimen Type V. The mechanicalproperties above are particularly well suited for articles that requireresiliency and flexibility, along with adequate wear strength and lowhygroscopicity.

Photopolymerizable compositions described herein can be mixed by knowntechniques. In some embodiments, for instance, a method for thepreparation of a photopolymerizable composition described hereincomprises the steps of mixing all or substantially all of the componentsof the photopolymerizable composition, heating the mixture, andoptionally filtering the heated mixture. Softening the mixture, in someembodiments, is carried out at a temperature of about 50° C. or in arange from about 50° C. to about 85° C. In some embodiments, aphotopolymerizable composition described herein is produced by placingall or substantially all components of the composition in a reactionvessel and heating the resulting mixture to a temperature ranging fromabout 50° C. to about 85° C. with stirring. The heating and stirring arecontinued until the mixture attains a substantially homogenized state.

Fabricating an Article

Once prepared as set forth above, the photopolymerizable compositions ofthe present disclosure may be used in myriad additive manufacturingprocesses to create a variety of articles, including casting a film asnoted above. A generalized method 100 for creating three-dimensionalarticles is illustrated in FIG. 1. Each step in the method will bediscussed in greater detail below.

First, in Step 110 the desired photopolymerizable composition (e.g.,comprising at least one urethane component, at least one monofunctionalreactive diluent, and an initiator) is provided and introduced into areservoir, cartridge, or other suitable container for use by or in anadditive manufacturing device. The additive manufacturing deviceselectively cures the photopolymerizable composition according to a setof computerized design instructions in Step 120. In Step 130, Step 110and/or Step 120 is repeated to form multiple layers to create thearticle comprising a three dimensional structure (e.g., an orthodonticaligner). Optionally uncured photopolymerizable composition is removedfrom the article in Step 140, further optionally, the article issubjected to additional curing to polymerize remaining uncuredphotopolymerizable components in the article in Step 150, and evenfurther optionally, the article is subjected to heat to drive offremaining unreacted reactive diluent in Step 160.

Methods of printing a three dimensional article or object describedherein can include forming the article from a plurality of layers of aphotopolymerizable composition described herein in a layer-by-layermanner. Further, the layers of a build material composition can bedeposited according to an image of the three dimensional article in acomputer readable format. In some or all embodiments, thephotopolymerizable composition is deposited according to preselectedcomputer aided design (CAD) parameters.

Additionally, it is to be understood that methods of manufacturing a 3Darticle described herein can include so-called “stereolithography/vatpolymerization” 3D printing methods. Other techniques forthree-dimensional manufacturing are known, and may be suitably adaptedto use in the applications described herein. More generally,three-dimensional fabrication techniques continue to become available.All such techniques may be adapted to use with photopolymerizablecompositions described herein, provided they offer compatiblefabrication viscosities and resolutions for the specified articleproperties. Fabrication may be performed using any of the fabricationtechnologies described herein, either alone or in various combinations,using data representing a three-dimensional object, which may bereformatted or otherwise adapted as necessary for a particular printingor other fabrication technology.

It is entirely possible to form a 3D article from a photopolymerizablecomposition described herein using vat polymerization (e.g.,stereolithography). For example, in some cases, a method of printing a3D article comprises retaining a photopolymerizable compositiondescribed herein in a fluid state in a container and selectivelyapplying energy to the photopolymerizable composition in the containerto solidify at least a portion of a fluid layer of thephotopolymerizable composition, thereby forming a hardened layer thatdefines a cross-section of the 3D article. Additionally, a methoddescribed herein can further comprise raising or lowering the hardenedlayer of photopolymerizable composition to provide a new or second fluidlayer of unhardened photopolymerizable composition at the surface of thefluid in the container, followed by again selectively applying energy tothe photopolymerizable composition in the container to solidify at leasta portion of the new or second fluid layer of the photopolymerizablecomposition to form a second solidified layer that defines a secondcross-section of the 3D article. Further, the first and secondcross-sections of the 3D article can be bonded or adhered to one anotherin the z-direction (or build direction corresponding to the direction ofraising or lowering recited above) by the application of the energy forsolidifying the photopolymerizable composition. Moreover, selectivelyapplying energy to the photopolymerizable composition in the containercan comprise applying actinic radiation, such as UV radiation, visibleradiation, or e-beam radiation, having a sufficient energy to cure thephotopolymerizable composition. A method described herein can alsocomprise planarizing a new layer of fluid photopolymerizable compositionprovided by raising or lowering an elevator platform. Such planarizationcan be carried out, in some cases, by utilizing a wiper or roller or arecoater bead. Planarization corrects the thickness of one or morelayers prior to curing the material by evening the dispensed material toremove excess material and create a uniformly smooth exposed or flatup-facing surface on the support platform of the printer.

It is further to be understood that the foregoing process can berepeated a selected number of times to provide the 3D article. Forexample, in some cases, this process can be repeated “n” number oftimes. Further, it is to be understood that one or more steps of amethod described herein, such as a step of selectively applying energyto a layer of photopolymerizable composition, can be carried outaccording to an image of the 3D article in a computer-readable format.Suitable stereolithography printers include the Viper Pro SLA, availablefrom 3D Systems, Rock Hill, S.C. and the Asiga Pico Plus39, availablefrom Asiga USA, Anaheim Hills, Calif.

FIG. 2 shows an exemplary stereolithography apparatus (“SLA”) that maybe used with the photopolymerizable compositions and methods describedherein. In general, the SLA 200 may include a laser 202, optics 204, asteering lens 206, an elevator 208, a platform 210, and a straight edge212, within a vat 214 filled with the photopolymerizable composition. Inoperation, the laser 202 is steered across a surface of thephotopolymerizable composition to cure a cross-section of thephotopolymerizable composition, after which the elevator 208 slightlylowers the platform 210 and another cross section is cured. The straightedge 212 may sweep the surface of the cured composition between layersto smooth and normalize the surface prior to addition of a new layer. Inother embodiments, the vat 214 may be slowly filled with liquid resinwhile an article is drawn, layer by layer, onto the top surface of thephotopolymerizable composition.

A related technology, vat polymerization with Digital Light Processing(“DLP”), also employs a container of curable polymer (e.g.,photopolymerizable composition). However, in a DLP based system, atwo-dimensional cross section is projected onto the curable material tocure the desired section of an entire plane transverse to the projectedbeam at one time. All such curable polymer systems as may be adapted touse with the photopolymerizable compositions described herein areintended to fall within the scope of the term “vat polymerizationsystem” as used herein. In certain embodiments, an apparatus adapted tobe used in a continuous mode may be employed, such as an apparatuscommercially available from Carbon 3D, Inc. (Redwood City, Calif.), forinstance as described in U.S. Pat. Nos. 9,205,601 and 9,360,757 (both toDe Simone et al.).

Referring to FIG. 5, a general schematic is provided of another SLAapparatus that may be used with photopolymerizable compositions andmethods described herein. In general, the apparatus 500 may include alaser 502, optics 504, a steering lens 506, an elevator 508, and aplatform 510, within a vat 514 filled with the photopolymerizablecomposition 519. In operation, the laser 502 is steered through a wall520 (e.g., the floor) of the vat 514 and into the photopolymerizablecomposition to cure a cross-section of the photopolymerizablecomposition 519 to form an article 517, after which the elevator 508slightly raises the platform 510 and another cross section is cured.

More generally, the photopolymerizable composition is typically curedusing actinic radiation, such as UV radiation, e-beam radiation, visibleradiation, or any combination thereof. The skilled practitioner canselect a suitable radiation source and range of wavelengths for aparticular application without undue experimentation.

After the 3D article has been formed, it is typically removed from theadditive manufacturing apparatus and rinsed, (e.g., an ultrasonic, orbubbling, or spray rinse in a solvent, which would dissolve a portion ofthe uncured photopolymerizable composition but not the cured, solidstate article (e.g., green body). Any other conventional method forcleaning the article and removing uncured material at the articlesurface may also be utilized. At this stage, the three-dimensionalarticle typically has sufficient green strength for handling in theremaining optional steps of method 100.

It is expected in certain embodiments of the present disclosure that theformed article obtained in Step 120 will shrink (i.e., reduce in volume)such that the dimensions of the article after (optional) Step 150 willbe smaller than expected. For example, a cured article may shrink lessthan 5% in volume, less than 4%, less than 3%, less than 2%, or evenless than 1% in volume, which is contrast to other compositions thatprovide articles that shrink about 6-8% in volume upon optionalpostcuring. The amount of volume percent shrinkage will not typicallyresult in a significant distortion in the shape of the final object. Itis particularly contemplated, therefore, that dimensions in the digitalrepresentation of the eventual cured article may be scaled according toa global scale factor to compensate for this shrinkage. For example, insome embodiments, at least a portion of the digital articlerepresentation can be at least 101% of the desired size of the printedappliance, in some embodiments at least 102%, in some embodiments atleast 104%, in some embodiments, at least 105%, and in some embodiments,at least 110%.

A global scale factor may be calculated for any given photopolymerizablecomposition formulation by creating a calibration part according toSteps 110 and 120 above. The dimensions of the calibration article canbe measured prior to postcuring.

In general, the three-dimensional article formed by initial additivemanufacturing in Step 120, as discussed above, is not fully cured, bywhich is meant that not all of the photopolymerizable material in thecomposition has polymerized even after rinsing. Some uncuredphotopolymerizable material is typically removed from the surface of theprinted article during a cleaning process (e.g., optional Step 140). Thearticle surface, as well as the bulk article itself, typically stillretains uncured photopolymerizable material, suggesting further cure.Removing residual uncured photopolymerizable composition is particularlyuseful when the article is going to subsequently be postcured, tominimize uncured residual photopolymerizable composition fromundesirably curing directly onto the article.

Further curing can be accomplished by further irradiating with actinicradiation, heating, or both. Exposure to actinic radiation can beaccomplished with any convenient radiation source, generally UVradiation, visible radiation, and/or e-beam radiation, for a timeranging from about 10 to over 60 minutes. Heating is generally carriedout at a temperature in the range of about 75-150° C., for a timeranging from about 10 to over 60 minutes in an inert atmosphere. Socalled post cure ovens, which combine UV radiation and thermal energy,are particularly well suited for use in the postcure process of Step150. In general, postcuring improves the mechanical properties andstability of the three-dimensional article relative to the samethree-dimensional article that is not postcured. In certain embodiments,the article is also subjected to heat to drive off remaining unreactedreactive diluent in Step 160.

The following describes general methods for creating a clear trayaligner as printed appliance 300. However, other dental and orthodonticarticles can be created using similar techniques and thephotopolymerizable compositions of the present disclosure.Representative examples include, but are not limited to, the removableappliances having occlusal windows described in InternationalApplication Publication No. WO2016/109660 (Raby et al.), the removableappliances with a palatal plate described in US Publication No.2014/0356799 (Cinader et al); and the resilient polymeric arch membersdescribed in International Application Nos. WO2016/148960 andWO2016/149007 (Oda et al.); as well as US Publication No. 2008/0248442(Cinader et al.). Moreover, the photopolymerizable compositions can beused in the creation of indirect bonding trays, such as those describedin International Publication No. WO2015/094842 (Paehl et al.) and USPublication No. 2011/0091832 (Kim, et al.) and other dental articles,including but not limited to crowns, bridges, veneers, inlays, onlays,fillings, and prostheses (e.g., partial or full dentures). Otherorthodontic appliances and devices include, but not limited to,orthodontic brackets, buccal tubes, lingual retainers, orthodonticbands, class II and class III correctors, sleep apnea devices, biteopeners, buttons, cleats, and other attachment devices.

In certain embodiments, the (e.g., orthodontic) article advantageouslyhas a certain equilibrium modulus even after stress relaxation providesa particular maximum amount of stress relaxation. The equilibriummodulus after stress relaxation can be measured by monitoring the stressresulting from a steady strain over time at a specific temperature(e.g., 37° C.) and a specific relative humidity (e.g., 100% relativehumidity). In at least certain embodiments, the equilibrium modulus is100 MPa or greater after 24 hours at 2% strain under 100% relativehumidity and 37° C.

Alternatively, the photopolymerizable compositions can be used in otherindustries, such as aerospace, animation and entertainment, architectureand art, automotive, consumer goods and packaging, education,electronics, hearing aids, sporting goods, jewelry, medical,manufacturing, etc.

Fabricating an Orthodontic Appliance with the PhotopolymerizableCompositions

One particularly interesting implementation of an article is generallydepicted in FIG. 3. The additive manufactured article 300 is a cleartray aligner and is removably positionable over some or all of apatient's teeth. In some embodiments, the appliance 300 is one of aplurality of incremental adjustment appliances. The appliance 300 maycomprise a shell having an inner cavity. The inner cavity is shaped toreceive and resiliently reposition teeth from one tooth arrangement to asuccessive tooth arrangement. The inner cavity may include a pluralityof receptacles, each of which is adapted to connect to and receive arespective tooth of the patient's dental arch. The receptacles arespaced apart from each other along the length of the cavity, althoughadjoining regions of adjacent receptacles can be in communication witheach other. In some embodiments, the shell fits over all teeth presentin the upper jaw or lower jaw. Typically, only certain one(s) of theteeth will be repositioned while others of the teeth will provide a baseor anchor region for holding the dental appliance in place as it appliesthe resilient repositioning force against the tooth or teeth to betreated.

In order to facilitate positioning of the teeth of the patient, at leastone of receptacles may be misaligned as compared to the correspondingtooth of the patient. In this manner, the appliance 300 may beconfigured to apply rotational and/or translational forces to thecorresponding tooth of the patient when the appliance 300 is worn by thepatient. In some particular examples, the appliance 300 may beconfigured to provide only compressive or linear forces. In the same ordifferent examples, the appliance 300 may be configured to applytranslational forces to one or more of the teeth within receptacles.

In some embodiments, the shell of the appliance 300 fits over some orall anterior teeth present in an upper jaw or lower jaw. Typically, onlycertain one(s) of the teeth will be repositioned while others of theteeth will provide a base or anchor region for holding the appliance inplace as it applies the resilient repositioning force against the toothor teeth to be repositioned. An appliance 300 can accordingly bedesigned such that any receptacle is shaped to facilitate retention ofthe tooth in a particular position in order to maintain the currentposition of the tooth.

A method 400 of creating an orthodontic appliance using thephotopolymerizable compositions of the present disclosure can includegeneral steps as outlined in FIG. 4. Individual aspects of the processare discussed in further detail below. The process includes generating atreatment plan for repositioning a patient's teeth. Briefly, a treatmentplan can include obtaining data representing an initial arrangement ofthe patient's teeth (Step 410), which typically includes obtaining animpression or scan of the patient's teeth prior to the onset oftreatment. The treatment plan will also include identifying a final ortarget arrangement of the patient's anterior and posterior teeth asdesired (Step 420), as well as a plurality of planned successive orintermediary tooth arrangements for moving at least the anterior teethalong a treatment path from the initial arrangement toward the selectedfinal or target arrangement (Step 430). One or more appliances can bevirtually designed based on the treatment plan (Step 440), and imagedata representing the appliance designs can exported in STL format, orin any other suitable computer processable format, to an additivemanufacturing device (e.g., a 3D printer system) (Step 450). Anappliance can be manufactured using a photopolymerizable composition ofthe present disclosure retained in the additive manufacturing device(Step 460).

In some embodiments, a (e.g., non-transitory) machine-readable medium isemployed in additive manufacturing of articles according to at leastcertain aspects of the present disclosure. Data is typically stored onthe machine-readable medium. The data represents a three-dimensionalmodel of an article, which can be accessed by at least one computerprocessor interfacing with additive manufacturing equipment (e.g., a 3Dprinter, a manufacturing device, etc.). The data is used to cause theadditive manufacturing equipment to create an article comprising areaction product of a photopolymerizable composition, thephotopolymerizable composition comprising a blend of: (a) 30 to 70 wt.%, inclusive, of at least one urethane component; (b) 25 to 70 wt. %,inclusive, of at least one monofunctional reactive diluent, wherein theat least one monofunctional reactive diluent comprises at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius; (c) optionally at least one difunctionalreactive diluent in an amount of 1 to 30 wt. %, inclusive, if present,based on the total weight of the photopolymerizable composition; (d) 0.1to 5 wt. %, inclusive, of at least one initiator; and (e) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present, basedon the total weight of the photopolymerizable composition. In certainembodiments, the article is an orthodontic article. Preferably, thearticle has an elongation at break of 25% or greater.

Data representing an article may be generated using computer modelingsuch as computer aided design (CAD) data. Image data representing the(e.g., polymeric) article design can be exported in STL format, or inany other suitable computer processable format, to the additivemanufacturing equipment. Scanning methods to scan a three-dimensionalobject may also be employed to create the data representing the article.One exemplary technique for acquiring the data is digital scanning. Anyother suitable scanning technique may be used for scanning an article,including X-ray radiography, laser scanning, computed tomography (CT),magnetic resonance imaging (MRI), and ultrasound imaging. Other possiblescanning methods are described, e.g., in U.S. Patent ApplicationPublication No. 2007/0031791 (Cinader, Jr., et al.). The initial digitaldata set, which may include both raw data from scanning operations anddata representing articles derived from the raw data, can be processedto segment an article design from any surrounding structures (e.g., asupport for the article). In embodiments wherein the article is anorthodontic article, scanning techniques may include, for example,scanning a patient's mouth to customize an orthodontic article for thepatient.

Often, machine-readable media are provided as part of a computingdevice. The computing device may have one or more processors, volatilememory (RAM), a device for reading machine-readable media, andinput/output devices, such as a display, a keyboard, and a pointingdevice. Further, a computing device may also include other software,firmware, or combinations thereof, such as an operating system and otherapplication software. A computing device may be, for example, aworkstation, a laptop, a personal digital assistant (PDA), a server, amainframe or any other general-purpose or application-specific computingdevice. A computing device may read executable software instructionsfrom a computer-readable medium (such as a hard drive, a CD-ROM, or acomputer memory), or may receive instructions from another sourcelogically connected to computer, such as another networked computer.Referring to FIG. 10, a computing device 1000 often includes an internalprocessor 1080, a display 1100 (e.g., a monitor), and one or more inputdevices such as a keyboard 1140 and a mouse 1120. In FIG. 10, an aligner1130 is shown on the display 1100.

Referring to FIG. 6, in certain embodiments, the present disclosureprovides a system 600. The system 600 comprises a display 620 thatdisplays a 3D model 610 of an article (e.g., an aligner 1130 as shown onthe display 1100 of FIG. 10); and one or more processors 630 that, inresponse to the 3D model 610 selected by a user, cause a 3Dprinter/additive manufacturing device 650 to create a physical object ofthe article 660. Often, an input device 640 (e.g., keyboard and/ormouse) is employed with the display 620 and the at least one processor630, particularly for the user to select the 3D model 610. The article660 comprises a reaction product of a photopolymerizable composition,the photopolymerizable composition comprising a blend of: (a) 30 to 70wt. %, inclusive, of at least one urethane component; (b) 25 to 70 wt.%, inclusive, of at least one monofunctional reactive diluent, whereinthe at least one monofunctional reactive diluent comprises at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius; (c) optionally at least one difunctionalreactive diluent in an amount of 1 to 30 wt. %, inclusive, if present,based on the total weight of the photopolymerizable composition; (d) 0.1to 5 wt. %, inclusive, of at least one initiator; and (e) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present, basedon the total weight of the photopolymerizable composition.

Referring to FIG. 7, a processor 720 (or more than one processor) is incommunication with each of a machine-readable medium 710 (e.g., anon-transitory medium), a 3D printer/additive manufacturing device 740,and optionally a display 730 for viewing by a user. The 3D printer /additive manufacturing device 740 is configured to make one or morearticles 750 based on instructions from the processor 720 providing datarepresenting a 3D model of the article 750 (e.g., an aligner 1130 asshown on the display 1100 of FIG. 10) from the machine-readable medium710.

Referring to FIG. 8, for example and without limitation, an additivemanufacturing method comprises retrieving 810, from a (e.g.,non-transitory) machine-readable medium, data representing a 3D model ofan article according to at least one embodiment of the presentdisclosure. The method further includes executing 820, by one or moreprocessors, an additive manufacturing application interfacing with amanufacturing device using the data; and generating 830, by themanufacturing device, a physical object of the article. The additivemanufacturing equipment can selectively cure a photopolymerizablecomposition to form an article. The article comprises a reaction productof a photopolymerizable composition, the photopolymerizable compositioncomprising a blend of: (a) 30 to 70 wt. %, inclusive, of at least oneurethane component; (b) 25 to 70 wt. %, inclusive, of at least onemonofunctional reactive diluent, wherein the at least one monofunctionalreactive diluent comprises at least one monofunctional reactive diluenthaving a T_(g) of up to but not including 25 degrees Celsius; (c)optionally at least one difunctional reactive diluent in an amount of 1to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition. One or more various optionalpost-processing steps 840 may be undertaken. Typically, remainingunpolymerized photopolymerizable component may be cured. In certainembodiments, the article comprises an orthodontic article. Preferably,the article exhibits an elongation at break of 25% or greater.Additionally, referring to FIG. 9, a method of making an articlecomprises receiving 910, by a manufacturing device having one or moreprocessors, a digital object comprising data specifying a plurality oflayers of an article; and generating 920, with the manufacturing deviceby an additive manufacturing process, the article based on the digitalobject. Again, the article may undergo one or more steps ofpost-processing 930, e.g., to cure unpolymerized urethane componentand/or reactive diluent remaining in the article. Typically, themanufacturing device selectively cures a photopolymerizable compositionto form the article.

Select Embodiments of the Disclosure

Embodiment 1 is a photopolymerizable composition. The photopolymerizablecomposition includes a blend of (a) 30 to 70 wt. %, inclusive, of atleast one urethane component and (b) 25 to 70 wt. %, inclusive, of atleast one monofunctional reactive diluent. The at least onemonofunctional reactive diluent includes at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius. The photopolymerizable composition further includes (c)optionally at least one multifunctional reactive diluent in an amount of1 to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

Embodiment 2 is the photopolymerizable composition of claim 1, whereinthe at least one urethane component is present in an amount of 50 to 70wt. %, inclusive, of the total weight of the photopolymerizablecomposition.

Embodiment 3 is the photopolymerizable composition of embodiment 1 orembodiment 2, wherein the at least one urethane component includes ahigh number average molecular weight (Mn) urethane component having oneor more urethane functionalities in the backbone of the compound and anumber average molecular weight of 1,000 grams per mole (g/mol) orgreater, with the proviso that all branches off the backbone of thecompound, if present, have a Mn of no more than 200 g/mol.

Embodiment 4 is the photopolymerizable composition of any of embodiments1 to 3, wherein the at least one urethane oligomer comprises a urethane(meth)acrylate, a urethane acrylamide, or combinations thereof, andwherein the at least one urethane component comprises a linking groupselected from alkyl, polyalkylene, polyalkylene oxide, aryl,polycarbonate, polyester, polyamide, and combinations thereof.

Embodiment 5 is the photopolymerizable composition of any of embodiments1 to 4, wherein the at least one urethane component includes a urethane(meth)acrylate comprising a polyalkylene oxide linking group, apolyamide linking group, or combinations thereof.

Embodiment 6 is the photopolymerizable composition of any of embodiments1 to 5, wherein the at least one monofunctional reactive diluent ispresent in an amount of 30 to 50 wt. %, inclusive, of the total weightof the photopolymerizable composition.

Embodiment 7 is the photopolymerizable composition of any of embodiments1 to 6, wherein the at least one monofunctional reactive diluentincludes a compatibilizer present in an amount of at least 30 wt. % ofthe amount of the at least one urethane component.

Embodiment 8 is the photopolymerizable composition of any of embodiments1 to 7, wherein the at least one monofunctional reactive diluent furtherincludes at least one monofunctional reactive diluent having a T_(g) of25 degrees Celsius or greater.

Embodiment 9 is the photopolymerizable composition of any of embodiments1 to 8, wherein the at least one monofunctional reactive diluentincludes each of at least one monofunctional reactive diluent having aT_(g) of up to but not including 25 degrees Celsius and at least onemonofunctional reactive diluent having a T_(g) of 25 degrees Celsius orgreater.

Embodiment 10 is the photopolymerizable composition of any ofembodiments 1 to 9, wherein the at least one monofunctional reactivediluent includes two monofunctional reactive diluents.

Embodiment 11 is the photopolymerizable composition of any ofembodiments 1 to 10, wherein the at least one monofunctional reactivediluent includes three monofunctional reactive diluents.

Embodiment 12 is the photopolymerizable composition of embodiment 10,wherein the at least one monofunctional reactive diluent includes onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius and two monofunctional reactive diluentshaving a T_(g) of 25 degrees Celsius or greater.

Embodiment 13 is the photopolymerizable composition of embodiment 10,wherein the at least one monofunctional reactive diluent includes twomonofunctional reactive diluents having a T_(g) of up to but notincluding 25 degrees Celsius and one monofunctional reactive diluenthaving a T_(g) of 25 degrees Celsius or greater.

Embodiment 14 is the photopolymerizable composition of any ofembodiments 1 to 13, wherein the at least one monofunctional reactivediluent includes a (meth)acrylate, an alkyl (meth)acrylate, a phenoxy(meth)acrylate, a hydroxy alkyl (meth)acrylate, or a combinationthereof.

Embodiment 15 is the photopolymerizable composition of any ofembodiments 1 to 14, wherein the at least one monofunctional reactivediluent includes phenoxy ethyl methacrylate.

Embodiment 16 is the photopolymerizable composition of embodiment 15,including phenoxy ethyl methacrylate in an amount of 20 to 80 wt. % ofthe total amount of the at least one monofunctional reactive diluent.

Embodiment 17 is the photopolymerizable composition of any ofembodiments 1 to 16, wherein the at least one multifunctional reactivediluent is present in an amount of 5 to 20 wt. %, inclusive, based onthe total weight of the photopolymerizable composition.

Embodiment 18 is the photopolymerizable composition of any ofembodiments 1 to 17, wherein the at least one multifunctional reactivediluent is present and comprises a polyester methacrylate.

Embodiment 19 is the photopolymerizable composition of any ofembodiments 1 to 18, wherein the at least one monofunctional reactivediluent includes a monofunctional reactive diluent exhibiting ahydrophilic-lipophilic balance (HLB) value of less than 10.

Embodiment 20 is the photopolymerizable composition of any ofembodiments 1 to 19, further including 0.01 to 1 wt. %, inclusive, of anabsorption modifier.

Embodiment 21 is the photopolymerizable composition of any ofembodiments 1 to 20, wherein the photopolymerizable composition has aviscosity at a temperature of 25 degrees Celsius of 10 Pa·s or less, asdetermined using a magnetic bearing rheometer using a 40 mm cone andplate measuring system at a shear rate of 0.1 1/s.

Embodiment 22 is the photopolymerizable composition of any ofembodiments 1 to 21, further including at least one filler.

Embodiment 23 is the photopolymerizable composition of any ofembodiments 1 to 22, further including at least one filler selected fromsilica, alumina, zirconia, and discontinuous fibers. Embodiment 24 isthe photopolymerizable composition of embodiment 23, wherein the silicaincludes surface-modified silica nanoparticles.

Embodiment 25 is the photopolymerizable composition of embodiment 22 orembodiment 23, wherein the discontinuous fibers include carbon, ceramic,glass, or combinations thereof.

Embodiment 26 is the photopolymerizable composition of any ofembodiments 1 to 25, wherein the at least one initiator includes a firstphotoinitiator.

Embodiment 27 is the photopolymerizable composition of embodiment 26,wherein the at least one initiator further includes a secondphotoinitiator.

Embodiment 28 is the photopolymerizable composition of embodiment 26 orembodiment 27, wherein the at least one initiator further includes athermal initiator.

Embodiment 29 is the photopolymerizable composition of any ofembodiments 1 to 28, wherein the at least one monofunctional reactivediluent is present in the form a prepolymer.

Embodiment 30 is the photopolymerizable composition of embodiment 29,wherein the prepolymer includes polymerization of up to 10%, up to 15%,or up to 20% of the functional groups of the at least one monofunctionalreactive diluent.

Embodiment 31 is the photopolymerizable composition of any ofembodiments 1 to 30, wherein the at least one urethane componentincludes at least one pendant group comprising a photoinitiator.

Embodiment 32 is an article including a reaction product of aphotopolymerizable composition. The photopolymerizable compositionincludes a blend of (a) 30 to 70 wt. %, inclusive, of at least oneurethane component and (b) 25 to 70 wt. %, inclusive, of at least onemonofunctional reactive diluent. The at least one monofunctionalreactive diluent includes at least one monofunctional reactive diluenthaving a T_(g) of up to but not including 25 degrees Celsius. Thephotopolymerizable composition further includes (c) optionally at leastone multifunctional reactive diluent in an amount of 1 to 30 wt. %,inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

Embodiment 33 is the article of embodiment 32, wherein the articlecomprises a plurality of layers.

Embodiment 34 is the article of embodiment 32 or embodiment 33,including a film or a shaped integral article.

Embodiment 35 is the article of any of embodiments 32 to 34, includingan orthodontic article.

Embodiment 36 is the article of any of embodiments 32 to 35, includingone or more channels, one or more undercuts, one or more perforations,or combinations thereof.

Embodiment 37 is the article of any of embodiments 32 to 36, exhibitingan elongation at break of 25% or greater.

Embodiment 38 is the article of any of embodiments 32 to 37, exhibitingan elongation at break of 40% or greater.

Embodiment 39 is the article of any of embodiments 32 to 38, exhibitinga tensile strength of 20 MegaPascals (MPa) or greater, as determinedaccording to ASTM D638-10.

Embodiment 40 is the article of any of embodiments 32 to 39, exhibitinga tensile strength of 30 MPa or greater, as determined according to ASTMD638-10.

Embodiment 41 is the article of any of embodiments 32 to 40, exhibitinga modulus of 500 MPa or greater, as determined according to ASTMD638-10.

Embodiment 42 is the article of any of embodiments 32 to 41, exhibitinga modulus of 1,000 MPa or greater, as determined according to ASTMD638-10.

Embodiment 43 is the article of any of embodiments 32 to 42, wherein theat least one urethane component is present in an amount of 50 to 70 wt.%, inclusive, of the total weight of the photopolymerizable composition.

Embodiment 44 is the article of any of embodiments 32 to 43, wherein theat least one urethane component includes a high number average molecularweight (Mn) urethane component having one or more urethanefunctionalities in the backbone of the compound and a number averagemolecular weight of 1,000 grams per mole (g/mol) or greater, with theproviso that all branches off the backbone of the compound, if present,have a Mn of no more than 200 g/mol.

Embodiment 45 is the article of any of embodiments 32 to 44, wherein theat least one urethane oligomer comprises a urethane (meth)acrylate, aurethane acrylamide, or combinations thereof, and wherein the at leastone urethane component comprises a linking group selected from alkyl,polyalkylene, polyalkylene oxide, aryl, polycarbonate, polyester,polyamide, and combinations thereof.

Embodiment 46 is the article of any of embodiments 32 to 45, wherein theat least one urethane component includes a urethane (meth)acrylatecomprising a polyalkylene oxide linking group, a polyamide linkinggroup, or combinations thereof.

Embodiment 47 is the article of any of embodiments 32 to 46, wherein theat least one monofunctional reactive diluent is present in an amount of30 to 50 wt. %, inclusive, of the total weight of the photopolymerizablecomposition.

Embodiment 48 is the article of any of embodiments 32 to 47, wherein theat least one monofunctional reactive diluent includes a compatibilizerpresent in an amount of at least 30 wt. % of the amount of the at leastone urethane component.

Embodiment 49 is the article of any of embodiments 32 to 48, wherein theat least one monofunctional reactive diluent further includes at leastone monofunctional reactive diluent having a T_(g) of 25 degrees Celsiusor greater.

Embodiment 50 is the article of any of embodiments 32 to 49, wherein theat least one monofunctional reactive diluent includes each of at leastone monofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius and at least one monofunctional reactivediluent having a T_(g) of 25 degrees Celsius or greater.

Embodiment 51 is the article of any of embodiments 32 to 50, wherein theat least one monofunctional reactive diluent includes two monofunctionalreactive diluents.

Embodiment 52 is the article of any of embodiments 32 to 51, wherein theat least one monofunctional reactive diluent includes threemonofunctional reactive diluents.

Embodiment 53 is the article of embodiment 52, wherein the at least onemonofunctional reactive diluent includes one monofunctional reactivediluent having a T_(g) of up to but not including 25 degrees Celsius andtwo monofunctional reactive diluents having a T_(g) of 25 degreesCelsius or greater.

Embodiment 54 is the article of embodiment 52, wherein the at least onemonofunctional reactive diluent includes two monofunctional reactivediluents having a T_(g) of up to but not including 25 degrees Celsiusand one monofunctional reactive diluent having a T_(g) of 25 degreesCelsius or greater.

Embodiment 55 is the article of any of embodiments 32 to 54, wherein theat least one monofunctional reactive diluent includes a (meth)acrylate,an alkyl (meth)acrylate, a phenoxy (meth)acrylate, a hydroxy alkyl(meth)acrylate, or a combination thereof.

Embodiment 56 is the article of any of embodiments 32 to 55, wherein theat least one monofunctional reactive diluent includes phenoxy ethylmethacrylate.

Embodiment 57 is the article of embodiment 56, comprising phenoxy ethylmethacrylate in an amount of 20 to 80 wt. % of the total amount of theat least one monofunctional reactive diluent.

Embodiment 58 is the article of any of embodiments 32 to 57, wherein theat least one multifunctional reactive diluent is present in an amount of5 to 20 wt. %, inclusive, based on the total weight of thephotopolymerizable composition.

Embodiment 59 is the article of any of embodiments 32 to 58, wherein theat least one multifunctional reactive diluent is present and comprises apolyester methacrylate.

Embodiment 60 is the article of any of embodiments 32 to 58, wherein theat least one monofunctional reactive diluent comprises a monofunctionalreactive diluent exhibiting a HLB value of less than 10.

Embodiment 61 is the article of any of embodiments 32 to 60, furtherincluding 0.01 to 1 wt. %, inclusive, of an absorption modifier.

Embodiment 62 is the article of any of embodiments 32 to 61, wherein thephotopolymerizable composition has a viscosity at a temperature of 25degrees Celsius of 10 Pa·s or less, as determined using a magneticbearing rheometer using a 40 mm cone and plate measuring system at ashear rate of 0.1 1/s.

Embodiment 63 is the article of any of embodiments 32 to 62, furtherincluding at least one filler.

Embodiment 64 is the article of any of embodiments 32 to 63, furtherincluding at least one filler selected from silica, alumina, zirconia,and discontinuous fibers.

Embodiment 65 is the article of embodiment 64, wherein the silicacomprises surface-modified silica nanoparticles.

Embodiment 66 is the article of embodiment 64 or embodiment 65, whereinthe discontinuous fibers include carbon, ceramic, glass, or combinationsthereof.

Embodiment 67 is the article of any of embodiments 32 to 66, wherein theat least one initiator includes a first photoinitiator.

Embodiment 68 is the article of embodiment 67, wherein the at least oneinitiator further includes a second photoinitiator.

Embodiment 69 is the article of embodiment 67 or embodiment 68, whereinthe at least one initiator further includes a thermal initiator.

Embodiment 70 is article of any of embodiments 32 to 69, wherein the atleast one urethane component includes at least one pendant groupcomprising a photoinitiator.

Embodiment 71 is a method of making an article is provided. The methodincludes (a) providing a photopolymerizable composition and (b)selectively curing the photopolymerizable composition to form anarticle. Optionally, the method further includes (c) curingunpolymerized urethane component and/or reactive diluent remaining afterstep (b). The photopolymerizable composition includes a blend of (a) 30to 70 wt. %, inclusive, of at least one urethane component and (b) 25 to70 wt. %, inclusive, of at least one monofunctional reactive diluent.The at least one monofunctional reactive diluent includes at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius. The photopolymerizable composition furtherincludes (c) optionally at least one multifunctional reactive diluent inan amount of 1 to 30 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition; (d) 0.1 to 5 wt. %,inclusive, of at least one initiator; and (e) an optional inhibitor inan amount of 0.001 to 1 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition.

Embodiment 72 is the method of embodiment 71, further including (d)repeating steps (a) and (b) to form multiple layers and create thearticle having a three dimensional structure prior to step (c).

Embodiment 73 is the method of embodiment 71 or embodiment 72, furtherincluding (e) subjecting the article to heating in an oven.

Embodiment 74 is the method of embodiment 73, wherein the oven is set ata temperature of 60 degrees Celsius or higher.

Embodiment 75 is the method of embodiment 73 or claim 74, wherein thearticle is subjected to stepwise heating at 60 degrees Celsius, 80degrees C., and then 100 degrees Celsius.

Embodiment 76 is the method of any of embodiments 73 to 75, wherein theoven comprises a vacuum oven.

Embodiment 77 is the method of any of embodiments 71 to 76, wherein thephotopolymerizable composition is cured using actinic radiationincluding UV radiation, e-beam radiation, visible radiation, or acombination thereof.

Embodiment 78 is the method of embodiment 77, wherein the radiation isdirected through a wall of a container holding the photopolymerizablecomposition.

Embodiment 79 is the method of any of embodiments 71 to 78, wherein thephotopolymerizable composition is cured through a floor of a containerholding the photopolymerizable composition.

Embodiment 80 is the method of any embodiments 71 to 79, furtherincluding postcuring the article using actinic radiation or heat.

Embodiment 81 is the method of any of embodiments 71 to 80, wherein themethod includes vat polymerization of the photopolymerizablecomposition.

Embodiment 82 is the method of any of embodiments 71 to 81, wherein theat least one initiator includes a first photoinitiator.

Embodiment 83 is the method of embodiment 82, wherein the at least oneinitiator further includes a second photoinitiator.

Embodiment 84 is the method of embodiment 82 or claim 83, wherein the atleast one initiator further includes a thermal initiator.

Embodiment 85 is the method of any of embodiments 71 to 84, wherein theat least one monofunctional reactive diluent is present in the form aprepolymer.

Embodiment 86 is the photopolymerizable composition of embodiment 85,wherein the prepolymer includes polymerization of up to 10%, up to 15%,or up to 20% of the functional groups of the at least one monofunctionalreactive diluent.

Embodiment 87 is the photopolymerizable composition of any ofembodiments 71 to 86, wherein the at least one urethane componentincludes at least one pendant group comprising a photoinitiator.

Embodiment 88 is a non-transitory machine readable medium. Thenon-transitory machine readable medium has data representing athree-dimensional model of an article, when accessed by one or moreprocessors interfacing with a 3D printer, causes the 3D printer tocreate an article. The article includes a reaction product of aphotopolymerizable composition including a blend of (a) 30 to 70 wt. %,inclusive, of at least one urethane component and (b) 25 to 70 wt. %,inclusive, of at least one monofunctional reactive diluent. The at leastone monofunctional reactive diluent includes at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius. The photopolymerizable composition further includes (c)optionally at least one multifunctional reactive diluent in an amount of1 to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

Embodiment 89 is a method. The method includes (a) retrieving, from anon-transitory machine readable medium, data representing a 3D model ofan article; (b) executing, by one or more processors, a 3D printingapplication interfacing with a manufacturing device using the data; and(c) generating, by the manufacturing device, a physical object of thearticle. The article includes a reaction product of a photopolymerizablecomposition including a blend of (a) 30 to 70 wt. %, inclusive, of atleast one urethane component and (b) 25 to 70 wt. %, inclusive, of atleast one monofunctional reactive diluent. The at least onemonofunctional reactive diluent includes at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius. The photopolymerizable composition further includes (c)optionally at least one multifunctional reactive diluent in an amount of1 to 30 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition; (d) 0.1 to 5 wt. %, inclusive, of atleast one initiator; and (e) an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.

Embodiment 90 is an article generated using the method of embodiment 89.

Embodiment 91 is the article of embodiment 90, wherein the articleincludes an orthodontic article.

Embodiment 92 is the article of embodiment 90 or embodiment 91,exhibiting an elongation at break of 25% or greater.

Embodiment 93 is a method. The method includes (a) receiving, by amanufacturing device having one or more processors, a digital objectcomprising data specifying a plurality of layers of an article; and (b)generating, with the manufacturing device by an additive manufacturingprocess, the article based on the digital object. The article includes areaction product of a photopolymerizable composition including a blendof (a) 30 to 70 wt. %, inclusive, of at least one urethane component and(b) 25 to 70 wt. %, inclusive, of at least one monofunctional reactivediluent. The at least one monofunctional reactive diluent includes atleast one monofunctional reactive diluent having a T_(g) of up to butnot including 25 degrees Celsius. The photopolymerizable compositionfurther includes (c) optionally at least one multifunctional reactivediluent in an amount of 1 to 30 wt. %, inclusive, if present, based onthe total weight of the photopolymerizable composition; (d) 0.1 to 5 wt.%, inclusive, of at least one initiator; and (e) an optional inhibitorin an amount of 0.001 to 1 wt. %, inclusive, if present, based on thetotal weight of the photopolymerizable composition.

Embodiment 94 is the method of embodiment 93, wherein the manufacturingdevice selectively cures a photopolymerizable composition to form anarticle.

Embodiment 95 is the method of embodiment 94, further including curingunpolymerized urethane component and/or reactive diluent, remaining inthe article.

Embodiment 96 is the method of any of embodiments 93 to 95, wherein thearticle includes an orthodontic article.

Embodiment 97 is the method of any of embodiments 93 to 96, wherein thearticle exhibits an elongation at break of 25% or greater.

Embodiment 98 is a system. The system includes (a) a display thatdisplays a 3D model of an article and (b) one or more processors that,in response to the 3D model selected by a user, cause a 3D printer tocreate a physical object of an article. The article includes a reactionproduct of a photopolymerizable composition including a blend of (a) 30to 70 wt. %, inclusive, of at least one urethane component and (b) 25 to70 wt. %, inclusive, of at least one monofunctional reactive diluent.The at least one monofunctional reactive diluent includes at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius. The photopolymerizable composition furtherincludes (c) optionally at least one multifunctional reactive diluent inan amount of 1 to 30 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition; (d) 0.1 to 5 wt. %,inclusive, of at least one initiator; and (e) an optional inhibitor inan amount of 0.001 to 1 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this disclosure.

TABLE 1A Materials. Description Source Tg (° C.) FunctionalityCrosslinking components: Exothane 108 Urethane Esstech Inc, — 2(meth)acrylate (Essington, PA, USA) oligomer Exothane 10 UrethaneEsstech Inc, — 2 (meth)acrylate (Essington, PA, USA) oligomer H1188Polyester Designer Molecules Inc, — 2 Methacrylate (San Diego, CA, USA)Monofunctional Reactive Diluents: EHMA Ethyl hexyl Alfa Aesar, −10  1methacrylate (Haverhill, MA, USA) PEMA Phenoxy Ethyl Sartomer 54 1Methacrylate, (Exton, PA, USA) SR340 IBoMA Isobornyl Sartomer (Exton,PA) 94 1 Methacrylate HEMA Hydroxyethyl Esstech Inc 57 1 Methacrylate(Essington, PA, USA) IBuMA Isobutyl TCI America, 20 1 Methacrylate(Portland OR, USA) Additives: BHT 2,6-Di-tert-butyl- Fluka Analytical —4-methyl-phenol (St. Louis, MO) TINOPAL 2,5-Thiophenediylbis(5- BASF,Wyandotte, MI — — OB tert-butyl-1,3- benzoxazole) (optical brightener)IRGAGURE 2,4,6-Trimethyl- BASF (Wyandotte, MI) — — TPObenzoyldiphenylphosphine oxide (photoinitiator)Unless otherwise noted, all printed Examples were printed on an AsigaPicoPlus39, a vat polymerization 3D printer available from Asiga USA,Anaheim Hills, Calif.

Measurement of HLB Values of the Monomer

HLB was obtained by the Griffin's method (See Griffin W C:“Calculationof HLB values of Non-ionic surfactants,” Journal of the Society ofCosmetic Chemists 5 (1954):259). The computations were conductedutilizing the software program Molecular Modeling Pro Plus from NorgwynMontgomery Software, Inc. (North Wales, Pa.).

TABLE 1B Hydrophilic-Lipophilic Balance (HLB) Values Compound MolecularWeight HLB 2-Ethyl Hexyl 3.39971 Methacrylate Hydroxyethyl 12.4469Methacrylate Isobutylmethacrylate 4.2239 Isobornyl 1.93492 methacrylatePhenoxyethyl 5.58884 methacrylate Exothane 10 13.764 H1188 5.32931 U8474.94337

Example 1 Preparation of Prepolymer Solution

Prepolymerization to make syrup (Si) was carried out by mixing 99.95parts free radical monomer(s) (IBuMA/EHMA/PEMA =1:1:1) with 0.05 partsof free radical initiator, (Irgacure TPO). The mixture was continuouslystirred using a magnetic stirrer and degassed by bubbling nitrogenthrough the solution for at least five minutes. The mixture was thenexposed to radiation from a blacklight for about 3 minutes. The reactionwas allowed to go to about 10-15% acrylate conversion.

Example 2

Preparation of Oligomer Solution with Pendant Photoinitiator

A preparation of PIEA was produced as the product of Irgacure 2959 and2-isocyanatoethylacrylate (IEA), according to the chemical reactionabove. Irgacure 2959 (50.29 g, 224.3 mmol) was dissolved in acetone (150mL, GFS Chemicals Inc., Powell, Ohio, USA). Di-n-butyltin dilaurate (0.5g, 0.8 mmol, Alfa Aesar, Tewksbury, Mass., 01876, USA) and BHT (0.2 g,0.9 mmol) were added, followed by the incremental addition of2-isocyanatoethyl acrylate (IEA, 3015 g, 213.6 mmol, Show Denko AmericaInc., N.Y., NY, USA), over 20 minutes with continuous stirring. Sampleswere taken and the IR spectrum was recorded. After 2-hour reaction time,NCO band (˜2200-2500 cm-1) disappeared indicating reaction completion.The solvent was removed in a rotary evaporator followed by furtherdrying under vacuum to give a hazy viscous liquid. The reaction yieldwas 99.7%.

A photo-initiator-carrying polymer (PP1) was prepared per the chemicalreaction above. Isobutylmethacrylate (10 g, 70,32 mmol, TCI America,Portland, Oreg., USA), 2-phenoxyethyl methacrylate (PEMA) (10.47 g,50.77 mmol, Sartomer Americas, Exton, Pa. USA), 2-ethyhexyl methacrylate(10.65 g , 53.71 mmol, TCI America), and PIEA (10.56 g, 28.9 mmol, anadduct of 2-isocyanatoethyl acrylate and Irgacure-2959) were dissolvedin isopropyl alcohol (75 mL, GFS Chemicals Inc., Powell, Ohio, USA) in a250 mL 3-neck flask equipped with an stirring bar, a condenser, athermocouple and a stream of N2 bubbling into the solution.2,2′-Azobis(2-methylpropionitrile) ((AIBN), 0.25 g, 1.5 mmol, SigmaAldrich, St Louis, Mo., USA) was added. After bubbling N2 through thesolution for 15 minutes, the heat was raised to 65° C. and stirredovernight. The next day, the heat was turned off and the solution wasallowed to cool to room temperature. The solvent was decanted off theproduct to obtain a moist product, which was then dried under vacuum togive a sticky semi-solid.

Example 3 Preparation of Nanofilled Exothane 10

400.0 grams of NALCO 2327 (NALCO, Naperville, Ill.), a 20 nm silicaaqueous nanodispersion, was placed in a 32 ounce clear glass jar. Themixture was agitated on a stir plate with a TEFLON coated stir bar.450.0 grams of 1-methoxy-2-propanol (Dow, Midland, Mich.) was slowlyadded to the jar. This was followed by addition of 11.00 grams of3-methacryloxypropyltrimethoxysilane (Gelest, Morrisville, Pa.) and 8.39grams of 3-cyanopropyltrimethoxysilane (Gelest, Morrisville, Pa.) to thejar. The nanodispersion in the jar was then mixed for an additional 20minutes. The stir bar was removed from the jar, and the jar was thentransferred to a solvent-rated oven at 80° C. for 24 hours. Thenanodispersion was then removed from the oven and allowed to cool toroom temperature. The nanodispersion was then transferred to a 2 litersingle neck flask round bottom flask. An amount of 330 grams of1-methoxy-2-propanol was added to the flask. The flask was sealed andthe nanodispersion was vigorously agitated to form a homogenous mixture.The flask was then attached to a ROTOVAP, and a solvent exchange wasperformed to remove water and create a solvent-based nanodispersion of˜41 weight percent solids in 1-methoxy-2-propanol. An amount of 36.5 gof surface treated nanosilica solution was mixed with 30 g of Exothane10. The mixture was heated in a ROTOVAP at 50° C. under continuousvacuum for 2 hours to remove the solvent. The final nanofilled Exothane10 mixture (NP1) had 33.33 wt % of silica nanoparticles.

Example 4 Preparation of Formulated Resins

Resins were prepared according to the formulations listed in Tables2A-2D below, by roller mixing the components overnight to ensurethorough mixing.

TABLE 2A Resin Formulations (grams) Example CE-1 CE-2 CE-3 CE-4 E-1 E-2E-3 Exothane 108 — — — — — — Exothane 10 80 20 — 50 50 50 50 H1188 — —50 — — — IBuMA 6.67 26.67 16.67 16.7 16.7 16.7 EHMA 6.67 26.67 16.67 1516.7 16.7 16.7 IBoMA — — — 30 — —  4.7 PEMA 6.67 26.67 16.67  5 — 16.712.5 HEMA — — — — 16.7 — — IRGACURE  2  2  2  2  2  2  2 TPO BHT  0.025 0.025  0.025  0.25  0.025  0.025  0.025

TABLE 2B Resin Formulations (grams) Example E-4 E-5 E-6 E-7 E-8 Exothane108 14.96 15.75 15.75 — — Exothane 10 34.89 47.25 47.25 37.5 63 Otheringredient 15 (NP1) — — — — H1188 — — 10 10 — U847 — — — 5 — IBuMA — — —— — EHMA 8.5 9 9 10 10.8 IBoMA 9.5 10 — — 10 PEMA 17.1 18 18 37.5 16.2IRGACURE 2 2 2 2 2 TPO BHT 0.025 0.025 0.025 0.025 0.025

TABLE 2C Resin Formulations (grams) EXAMPLES E-9-E13 Example E-9 E-10E-11 E12 E13 Exothane 108 — — — — 30 Exothane 10 70 40 50 30 — H1188 —10 — 10 20 U847 — — — 10 — IBuMA — — — 16.7 15 EHMA 12 15 10 16.7 15IBoMA — — — — — PEMA 18 35 40 16.7 15 HEMA — — — — — IRGACURE  2  2  2 2 2 TPO BHT    0.025    0.025    0.025 0.025    0.025

TABLE 2D Resin Formulations (grams) EXAMPLES E-14-E-16 Example E-14 E-15E-16 Exothane 108 — — — Exothane 10 40 40 50 H1188 10 10 — Special — 50(S1) 10 (PP1) ingredient IBuMA 16.7 — 13.33 EHMA 16.7 — 13.33 IBoMA — —— PEMA 16.7 — 13.33 HEMA — — — IRGACURE 2 2 2 TPO BHT 0.025 0.025 0.025

Example 5 Viscosity of the Resins

Absolute (e.g., dynamic) viscosities of the example resins were measuredusing a TA Instruments AR-G2 magnetic bearing rheometer using a 40millimeter cone and plate measuring system at 40 ° C. at a shear rate of0.1 1/s. Two replicates were measured and the average value was reportedas the viscosity, in Pa·s, in Table 3 below.

TABLE 3 Viscosities of Example resins in Pa · s. Sample ID Viscosity (Pa· s) CE-1 Too viscous to be printable CE-2 0.176 CE-3 0.275 CE-4 Notcompatible, phase separated E-1 0.181 E-2 0.152 E-3 0.298 E-4 2.33  E-51.478 E-6 3.39  E-7 0.331 E-8 1.865 E-9 2.766 E-10 0.251 E-11 0.410 E-120.167 E-13 0.215 E-14 0.277 E-15 0.508 E-16 0.163

Example 6

Physical Properties of Polymers from Cast Resin Formulations

The Example 1 (E-1) formulation shown in Table 2A was mixed in a glassjar. The E-1 mixture was placed on a rolling mixer to make a homogenousmixture. The mixture was degassed and speed mixed in THINKY planetarymixer (Thinky Corporation, Tokyo, Japan), at 2000 rpm for 90 secondsunder vacuum. The mixture was then poured in a silicone dogbone mold(Type V mold, ASTM D638-10). For modulus measurements, a rectangularpiece of dimensions (12 mm×63.5 mm×1 mm) was cast in a silicone mold.The filled mold was placed between two glass plates and cured in AsigaPico Flash post-curing device for 15 minutes. The sample was demoldedand cured for another 15 minutes in the chamber. The dogbones were keptin a vacuum oven at 100° C. overnight to remove any residual unreactedmonomer. These dogbones were tested on an Insight MTS with 5 kN loadcell at the rate of 5 mm/minute. Five replicate samples were tested, andthe average and standard deviation are reported. The tensile strengthwas determined according to ASTM D638-10 and shown in Table 4 below.Elongation at break was determined from the crosshead movement of thegrips and the samples were not strain gauged. For modulus, the modulusrectangular samples were pulled in tension at the rate of 1 mm/min until5% strain was achieved. The initial slope of the stress-strain curve isreported as the modulus of the part.

Subsequent examples, E-2-E-15 and CE-1-CE-3, were made by the samemethod (the formulations for these examples are summarized in Tables2A-2D above) and tested. For E-16 an additional UV cure for 10 mins wasdone in presence of germicidal lamp (GE G30T8, 30 W bulb). The testresults of the cast samples are summarized in Table 4 below.

TABLE 4 Tensile strength (MPa), Tensile Modulus (MPa) and Elongation atbreak (%) of Cast Formulations. Crosshead Tensile Tensile ElongationStrength Modulus at Break Sample ID (Std Dev) (Std Dev) (Std Dev) CE-147.8 (0.38) 1122.8 48.2 (30.1) CE-2 10.9 (0.8) — 188.9 (15.2) CE-3 59.1(4.6) — 7.7 (1) CE-4 Phase separated — — E-1 48.4 (0.58) 62.2 (27.2) E-232.3 (1) 991.4 101 (20.5) E-3 35.8 (0.9) 55.2 (25.6) E-4 37.7 (1) 1374.997.5 (17.9) 5 wt % nanofilled E-5 37.1 (0.4) 1169.2 99.6 (19.5) E-6 39.7(0.6) 1288.4 62 (13.3) E-7 46.0 (1.3) 1359.8 51 (13.5) E-8 41.4 (2.4)1306.9 42.2 (27.3) E-9 41.9 (0.7) 1323 74.3 (25.2) E-10 45.1 (0.6)1164.7 47.5 (13.6) E-11 39.1 (1.1) 1254.3 60.3 (43.3) E-12 33.2 (2.1)823.4 50.3 (16.3) E-13 30.6 (1.9) 976.4 44.1 (10.4) E-14 40.3 (0.6)1214.2 47.5 (12.2) E-15 41.3 (0.6) 1284.8 23 (7.3) E-16 34.4 (0.8)1205.8 98 (7.2)

Example 7 Additive Manufacturing of 3D Printed Parts

The formulations of E-1, E-2, E-3, E-14 and E-15 resins werephotopolymerized on the Asiga Pico 2 printer with a LED light source of385 nm and ˜23 mW/cm2 of power. Tensile test bars of Type V according toASTM D638-10 were manufactured. The following settings were used: Slicethickness=50 μm, Burn-In Layers=1, Separation Velocity=10 mm/s, Slidesper Layer=1, Burn-In Exposure Time=20.0 s, Normal Exposure Time=3.5 s.The test bars were then cleaned in isopropanol to remove unreactedresin. The test bars were then post-cured under fusion lamps for 90minutes on each side. The dogbones were kept in a vacuum oven at 80° C.overnight to remove any residual unreacted monomer. The post-cureddogbones were tested on an Insight MTS with 5 kN load cell at the rateof 5 mm/minute. Five replicate samples were tested, and the average andstandard deviation are reported. The tensile strength of the samples wasdetermined according to ASTM D638-10 and shown in Table 5 below.Elongation at break was determined from the crosshead movement of thegrips and the samples were not strain gauged.

TABLE 5 Tensile strength (MPa), Tensile Modulus (MPa) and Elongation atbreak (%) of 3D printed Formulations Crosshead Tensile TensileElongation Strength Modulus at Break Sample ID (Std Dev) (Std Dev) (StdDev) E-1 43.2 (02) 1552 93.4 (35.3) E-2 32.5 (0.8) 1090 114.7 (24.5) E-339.2 (0.3) 1091.6 80.1 (23.6) E-14 39.2 (0.6) — 47.8 (9) E-15 40.3 (0.4)1228.3 19 (11.5)

Example 8

Quantifying Amount of Residual Monomers after Printing

E-3 squares (20 mm×20 mm×1 mm) were printed using the method describedin Example 7. The printed samples (printed) were wiped with a KIMWIPE toremove excess residual monomer. The parts were post-cured under fusionlamps for 90 minutes on each side (postcured). The post-cured sampleswere then baked in the oven for 4 hours at 120° C. under vacuum toremove any residual unreacted monomers (baked). The percent unreactedmonomers were quantified gravimetrically. Three squares at each stagewere heated in the oven at 120° C. for 4 hours and the weight loss afterthat was reported as % residuals.

TABLE 6 Percent Residual Amount of Monomers for E-3 Printed SquaresStage % Residuals Monomer (Std Dev) Printed 2.86 (0.19) Postcured 0.53(0.02) Baked 0.00 (0)  

Example 9 Printing of Orthodontic Clear Tray Aligner

The formulation of E-2 was photopolymerized on the Asiga Pico 2 HDprinter with a LED light source of 385 nm and ˜16 mW/cm² of power. AnSTL file of the aligner was loaded into the software and supportstructures were generated. The resin bath of the printer was heated to35-40° C. before photopolymerization to reduce the viscosity to be ableto manufacture the article. The following settings were used: Slicethickness=50 μm, Burn-In Layers=1, Separation Velocity=10 mm/s, Slidesper Layer=1, Burn-In Exposure Time=20.0 s, Normal Exposure Time=3.5 s.The photopolymerized aligners were then cleaned in isopropanol to removeunreacted resin and then post-cured under fusion lamps for 90 minutes oneach side. The aligners were baked stepwise in a vacuum oven—30 minutesat 60° C., 1 hour at 80° C. followed by 4 hours at 100° C. to remove anyunreacted monomers. The photopolymerized aligners fit the models,showing precision of the additive manufacture part. The aligners alsohad acceptable strength and flexibility.

All of the patents and patent applications mentioned above are herebyexpressly incorporated by reference. The embodiments described above areillustrative of the present invention and other constructions are alsopossible. Accordingly, the present invention should not be deemedlimited to the embodiments described in detail above and shown in theaccompanying drawings, but instead only by a fair scope of the claimsthat follow along with their equivalents.

1. A photopolymerizable composition comprising a blend of: a. 30 to 70wt. %, inclusive, of at least one urethane component; b. 25 to 70 wt. %,inclusive, of at least one monofunctional reactive diluent, wherein theat least one monofunctional reactive diluent comprises at least onemonofunctional reactive diluent having a T_(g) of up to but notincluding 25 degrees Celsius and wherein i) the at least onemonofunctional reactive diluent comprises phenoxy ethyl methacrylate inan amount of 20 to 80 wt. % of the total amount of the at least onemonofunctional reactive diluent, or ii) the at least one monofunctionalreactive diluent is present in the form a prepolymer, or both i) andii), and wherein the at least one monofunctional reactive diluentfurther comprises at least one monofunctional reactive diluent having aT_(g) of 25 degrees Celsius or greater; c. optionally at least onemultifunctional reactive diluent in an amount of 1 to 30 wt. %,inclusive, if present, based on the total weight of thephotopolymerizable composition; d. 0.1 to 5 wt. %, inclusive, of atleast one initiator; and e. an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.
 2. The photopolymerizable composition ofclaim 1, wherein the at least one urethane oligomer comprises a urethane(meth)acrylate, a urethane acrylamide, or combinations thereof, andwherein the at least one urethane component comprises a linking groupselected from alkyl, polyalkylene, polyalkylene oxide, aryl,polycarbonate, polyester, polyamide, and combinations thereof.
 3. Thephotopolymerizable composition of claim 1, wherein the at least onemonofunctional reactive diluent comprises a compatibilizer present in anamount of at least 30 wt. % of the amount of the at least one urethanecomponent.
 4. (canceled)
 5. The photopolymerizable composition of claim1, wherein the at least one monofunctional reactive diluent comprises a(meth)acrylate, an alkyl (meth)acrylate, a phenoxy (meth)acrylate, ahydroxy alkyl (meth)acrylate, or a combination thereof.
 6. Thephotopolymerizable composition of claim 1, wherein the at least onemonofunctional reactive diluent comprises phenoxy ethyl methacrylate inan amount of 20 to 80 wt. % of the total amount of the at least onemonofunctional reactive diluent.
 7. The photopolymerizable compositionof claim 1, wherein the at least one multifunctional reactive diluent ispresent and comprises a polyester methacrylate.
 8. Thephotopolymerizable composition of claim 1, wherein the at least onemonofunctional reactive diluent comprises a monofunctional reactivediluent exhibiting a hydrophilic-lipophilic balance (HLB) value of lessthan
 10. 9. The photopolymerizable composition of claim 1, wherein theat least one initiator comprises a photoinitiator, a thermal initiator,or a combination thereof.
 10. The photopolymerizable composition ofclaim 1, wherein the at least one monofunctional reactive diluent ispresent in the form a prepolymer.
 11. The photopolymerizable compositionof claim 1, wherein the at least one urethane component comprises atleast one pendant group comprising a photoinitiator.
 12. An articlecomprising a reaction product of a photopolymerizable composition,wherein the photopolymerizable composition comprises a blend of: a. 30to 70 wt. %, inclusive, of at least one urethane component; b. 25 to 70wt. %, inclusive, of at least one monofunctional reactive diluent,wherein the at least one monofunctional reactive diluent comprises atleast one monofunctional reactive diluent having a T_(g) of up to butnot including 25 degrees Celsius and wherein i) the at least onemonofunctional reactive diluent comprises phenoxy ethyl methacrylate inan amount of 20 to 80 wt. % of the total amount of the at least onemonofunctional reactive diluent, or ii) the at least one monofunctionalreactive diluent is present in the form a prepolymer, or both i) andii), and wherein the at least one monofunctional reactive diluentfurther comprises at least one monofunctional reactive diluent having aT_(g) of 25 degrees Celsius or greater; c. optionally at least onedifunctional reactive diluent in an amount of 1 to 30 wt. %, inclusive,if present, based on the total weight of the photopolymerizablecomposition; d. 0.1 to 5 wt. %, inclusive, of at least one initiator;and e. an optional inhibitor in an amount of 0.001 to 1 wt. %,inclusive, if present, based on the total weight of thephotopolymerizable composition.
 13. The article of claim 12, wherein thearticle comprises a plurality of layers.
 14. The article of claim 12,comprising an orthodontic article.
 15. The article of claim 12,exhibiting an elongation at break of 40% or greater.
 16. The article ofclaim 12, exhibiting a tensile strength of 20 MegaPascals (MPa) orgreater, as determined according to ASTM D638-10.
 17. The article ofclaim 12, exhibiting a modulus of 500 MPa or greater, as determinedaccording to ASTM D638-10.
 18. (canceled)
 19. (canceled)
 20. Anon-transitory machine readable medium comprising data representing athree-dimensional model of an article, when accessed by one or moreprocessors interfacing with a 3D printer, causes the 3D printer tocreate an article comprising a reaction product of a photopolymerizablecomposition comprising a blend of: a. 30 to 70 wt. %, inclusive, of atleast one urethane component; b. 25 to 70 wt. %, inclusive, of at leastone monofunctional reactive diluent, wherein the at least onemonofunctional reactive diluent comprises at least one monofunctionalreactive diluent having a T_(g) of up to but not including 25 degreesCelsius and wherein i) the at least one monofunctional reactive diluentcomprises phenoxy ethyl methacrylate in an amount of 20 to 80 wt. % ofthe total amount of the at least one monofunctional reactive diluent, orii) the at least one monofunctional reactive diluent is present in theform a prepolymer, or both i) and ii), and wherein the at least onemonofunctional reactive diluent further comprises at least onemonofunctional reactive diluent having a T_(g) of 25 degrees Celsius orgreater; c. optionally at least one difunctional reactive diluent in anamount of 1 to 30 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition; d. 0.1 to 5 wt. %,inclusive, of at least one initiator; and e. an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present, based on the totalweight of the photopolymerizable composition.
 21. (canceled)
 22. Amethod comprising: a. receiving, by a manufacturing device having one ormore processors, a digital object comprising data specifying a pluralityof layers of an article; and b. generating, with the manufacturingdevice by an additive manufacturing process, the article based on thedigital object, the article comprising a reaction product of aphotopolymerizable composition, the photopolymerizable compositioncomprising a blend of: i. 30 to 70 wt. %, inclusive, of at least oneurethane component; ii. 25 to 70 wt. %, inclusive, of at least onemonofunctional reactive diluent, wherein the at least one monofunctionalreactive diluent comprises at least one monofunctional reactive diluenthaving a T_(g) of up to but not including 25 degrees Celsius and whereini) the at least one monofunctional reactive diluent comprises phenoxyethyl methacrylate in an amount of 20 to 80 wt. % of the total amount ofthe at least one monofunctional reactive diluent, or ii) the at leastone monofunctional reactive diluent is present in the form a prepolymer,or both i) and ii), and wherein the at least one monofunctional reactivediluent further comprises at least one monofunctional reactive diluenthaving a T_(g) of 25 degrees Celsius or greater; iii. optionally atleast one difunctional reactive diluent in an amount of 1 to 30 wt. %,inclusive, if present, based on the total weight of thephotopolymerizable composition; iv. 0.1 to 5 wt. %, inclusive, of atleast one initiator; and v. an optional inhibitor in an amount of 0.001to 1 wt. %, inclusive, if present, based on the total weight of thephotopolymerizable composition.
 23. (canceled)